Cell bio enzymes 1 & 2 Flashcards
IMP IMP IMP!!!!!
SALIVARY GLANDS
enzymes:
- ? (Ptyalin): amylose (polysaccharide) ->
- ? lipase: Lipids (TAG, cholesterol) -> ?
STOMACH
enzymes:
1. ? (protease): proteins ->
2. ? lipase: Lipids (TAG, cholesterol) -> ?
PANCREAS
enzymes:
1. ?: Polysaccharides > disaccharides
2. Trypsin (protease): Proteins -> ?
3. ? (protease): Proteins -> peptides
4. ?: Lipids -> DAG, MAG, FFA, glycerol
SMALL INTESTINE BRUSH BORDER
1. peptidases: Polypeptides -> ?
2. nucleotidases: ? -> nucleotides, ribose
3. lactase: Disaccharides -> ?
4. maltase: ? -> monosaccharides
5. sucrase: ? -> monosaccharides
ENSURE TO TEST YOURSELF ON THIS!
DR. CAMARGO SAID “U MUST KNOW ALL OF IT!!”
IMP IMP IMP!!!!!
SALIVARY GLANDS
enzymes:
- alpha-amylase (Ptyalin): amylose (polysaccharide) ->
- lingual lipase: Lipids (TAG, cholesterol) -> ?
STOMACH
enzymes:
1. pepsin (protease): proteins -> peptides
2. gastric lipase: Lipids (TAG, cholesterol) -> DAG, MAG, FFA, glycerol
PANCREAS
enzymes:
1. pancreatic amylase: Polysaccharides > disaccharides
2. Trypsin (protease): Proteins -> peptides
3. chymotrypsin (protease): Proteins -> peptides
4. acid : Lipids -> DAG, MAG, FFA, glycerol
SMALL INTESTINE BRUSH BORDER
1. peptidases: Polypeptides -> amino acids
2. nucleotidases: DNA, RNA -> nucleotides, ribose
3. lactase: Disaccharides -> monosaccharides
4. maltase: Disaccharides -> monosaccharides
5. sucrase: Disaccharides -> monosaccharides
Most all diseases in animals are manifestations of abnormalities in:
- ?
- ?
- ?
Most all diseases in animals are manifestations of abnormalities in:
- biomolecules
- chemical rxns
- biochemical pathways
ENZYMES
Enzymes are ? that act as ? by accelerating chemical reactions.
The molecules upon which enzymes may act are called ?, and the enzyme converts the substrates into different molecules known as ?.
They have a ? for their substrates, and they accelerate chemical reactions tremendously, without being ? or used up during the process (?).
Generally, a small amount of enzyme will influence a ? of reactive substrate.
Act as ? for virtually all chemical reactions in biological systems, playing fundamental roles in metabolic events, ? and cell regulation.
ENZYMES
Enzymes are proteins that act as biological catalysts by accelerating chemical reactions.
The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products.
They have a high degree for their substrates, and they accelerate chemical reactions tremendously, without being changed or used up during the process (reversible binding).
Generally, a small amount of enzyme will influence a large amount of reactive substrate.
Act as mediators for virtually all chemical reactions in biological systems, playing fundamental roles in metabolic events, signal transduction and cell regulation.
in the image: E = enzyme; S = substrate ES=enzyme substrate complex; P = product
ENZYMES
The binding is very ?, small changes in the shape of the ligand/substrate (key) can cause major change in protein (lock) behavior.
Complementary shape: ? function, plays a major role in ?
[story: enzyme is the lock and substrate is the key (thus substrate seeks help from the Goddess enzyme and goddess enzyme fulfills substrate’s wish i.e., to create a product)]
?: the ability of a protein to change shape, resulting in a change in binding affinity at a different binding site.
Allosteric enzymes: have the ? site, as well as an ? site (allosteric site) *
(From the Greek ‘allo’, which means ‘other’.)
“shape influences binding, and in turn, binding can influence shape”
ENZYMES
The binding is very specific, small changes in the shape of the ligand/substrate (key) can cause major change in protein (lock) behavior.
Complementary shape: recognition function, plays a major role in information transfer
ALLOSTERY: the ability of a protein to change shape, resulting in a change in binding affinity at a different binding site.
Allosteric enzymes: have the binding site, as well as an additional site (allosteric site) *
(From the Greek ‘allo’, which means ‘other’.)
“shape influences binding, and in turn, binding can influence shape”
LIFE DEPENDS ON A COMPLEX NETWORK OF CHEMICAL REACTIONS
? metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to ? life.
Binding sites of enzymes are usually very specific for a particular ?/? and the binding is ?.
[some enzymes have diff. active sites and each active site will have their own specific binding site to which appropriate substrates will bind to]
almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life.
The binding sites of enzymes are usually very specific for a particular ligand/substrate and the binding is reversible.
INDUSTRIAL FIELDS ALSO BENEFITS FROM ENZYMES
* ? production (biodiesel, alcohol from sugar cane)
* ? (animal feed additives, fertilizers…)
* Fermentations: transformation of raw materials such as ? etc. in industrial mixtures such as liquors, brewing
* ?: transformation of defined precursors to a desired target product
o Environmentally friendly processes to treat ? (some fungi being used to degrade ?)
* Pharmaceutical industry: synthesis & modification of ?
* ? of disease: increased or decreased concentrations of enzyme activity in the target system (liver, kidney, muscle)
* Treatment of disease: i.e. use of ? to dissolve blood clots
sidenotes:
in brazil most cars move from alcohol made from sugar cane
INDUSTRIAL FIELDS ALSO BENEFITS FROM ENZYMES
* biofuel production (biodiesel, alcohol from sugar cane)
* agricultural (animal feed additives, fertilizers…)
* Fermentations: the transformation of raw materials such as sugar, starch etc. in industrial mixtures such as liquors, brewing
* biotransformation: transformation of defined precursors to a desired target product
o Environmentally friendly processes to treat waste (some fungi being used to degrade waste)
* Pharmaceutical industry: synthesis & modification of medicines, antibiotics
* diagnosis of disease: increased or decreased concentrations of enzyme activity in the target system (liver, kidney, muscle)
* Treatment of disease: i.e. use of streptokinase to dissolve blood clots
INDUSTRIAL ENZYMES AND THEIR USES
*IMP!
1. protease: degradation of ? -> detergents
2. cellulase: degradation of ? -> detergents
3. lipase: degradation of ? -> detergents
IMP. TO KNOW THIS (when working in vaccines, sanitizing things so using detergents thus need to know what each type of detergent so it doesn’t clash w each other)*
HOW ENZYMES WORK?
* Chemical reactions have an ? separating the reactants and the products.
* Energy is needed to get them started = known as ?
* Enzymes greatly ? the activation energy ? that block chemical reactions.
NDUSTRIAL ENZYMES AND THEIR USES
- protease: degradation of proteins -> detergents
- cellulase: degradation of cellulose -> detergents
- lipase: degradation of lipids -> detergents
IMP. TO KNOW THIS (when working in vaccines, sanitizing things so using detergents thus need to know what each type of detergent so it doesn’t clash w each other)
HOW ENZYMES WORK?
* Chemical reactions have an energy barrier separating the reactants and the products.
* Energy is needed to get them started = known as activation energy
* Enzymes greatly reduce the activation energy barrier that block chemical reactions.
HOW ENZYMES WORK?
Enzymes ? molecules through a specific ? pathway
* allowing a reaction to proceed ? by providing an ? reaction pathway in the cell which has a lower activation energy.
Enzymes show a ? and usually catalyze ? specific reaction, or a set of ? reactions; directing a particular reaction pathway.
THE TRANSITION STATE
* The ? acts as a molecular template that binds the substrate and initiates its conversion to the ?
- The ? state is the form the substrate must take before it becomes ?.
- It is the ? energy point of the reaction.
? the transition state (T) an enzyme can greatly increase the ? of the reactive intermediate that can be converted to product thus accelerating the reaction.
HOW ENZYMES WORK?
Enzymes direct substrate molecules through a specific reaction pathway
* allowing a reaction to proceed rapidly by providing an alternate reaction pathway in the cell which has a lower activation energy.
Enzymes show a high selectivity and usually catalyze only one specific reaction, or a set of closely related reactions; directing a particular reaction pathway.
THE TRANSITION STATE
* The active site acts as a molecular template that binds the substrate and initiates its conversion to the transition state
- The transition state is the form the substrate must take before it becomes product
- It is the highest energy point of the reaction.
- stabilizing the transition state (T*) an enzyme can greatly increase the concentration of the reactive intermediate that can be converted to product thus accelerating the reaction.
NOMENCLATURE
Recommended name: short name, most used, has the suffix ‘-ase’ attached to
[enzyme named a/c to substrates, description of rxn and full names for scientific papers]
- the “ ? “ of the reaction: i.e., “Gluco”kinase (found mostly in liver and pancreas, phosphorylation of glucose)
- the “ ? “ of the reaction performed: i.e., Lactate “dehydrogen”ase
” ? “: more complete, complex; is used when an enzyme must be identified without ? (used in scientific papers)
The suffix -ase is attached to a more complete description of the chemical reaction catalyzed, including the “names of all substrates”: e.g. LDH (lactate dehydrogenase): Lactate, NAD+oxidoreductase
The systematic names are unambiguous and informative, but often too big for general use
NOMENCLATURE
Recommended name: short name, most used, has the suffix ‘-ase’ attached to
[enzyme named a/c to substrates, description of rxn and full names for scientific papers]
- the “substrate” of the reaction: i.e., “Gluco”kinase (found mostly in liver and pancreas, phosphorylation of glucose)
- the “description” of the reaction performed: i.e., Lactate “dehydrogen”ase
“systemic name”: more complete, complex; is used when an enzyme must be identified without ambiguity (used in scientific papers)
The suffix -ase is attached to a more complete description of the chemical reaction catalyzed, including the “names of all substrates”: e.g. LDH (lactate dehydrogenase): Lactate, NAD+oxidoreductase
The systematic names are unambiguous and informative, but often too big for general use
*imp!
Pepsin
substrate: ?
products: short polypeptides
Rennin
substrate: soluble ? (milk protein)
product: ? (curdled milk)*
MAJOR CLASSES OF ENZYME
- Oxidoreductases: catalyze reactions in which one molecule is ? while the other is ?, transfer of electrons (e-) and ?
e.g. of enzymes: oxidases, ?, dehydrogenases, ?
(lactate dehydrogenase (NAD+ -> NADH + H)) - Transferases: transfer carbon, ? or ? groups
e.g. methyltransferases, ?, kinases, ? (serine hydroxymethyl transferase: serine -> glycine and CH2) - Hydrolases: enzymes that catalyze a ? reaction (use water to break a chemical bond) *most ? are hydrolases as they (e.g. lipase) which need to reach the hydrophobic part of lipids need water around to break down the chemical bond
e.g. nucleases, ?, phosphatases (urease: urea -> carbon di oxide and ammonia) - Lyases: catalyze the cleavage of ? bonds
(catalyzes the breaking of various chemical bonds by means other than ? and ?, often forming a new double bond or a new ring structure)
e.g. decarboxylases, ?, synthases, ? (e.g. pyruvate decarboxylate: pyruvate -> acetaldehyde) - Isomerases: catalyze the ? of bonds within a ? molecule, transfer of groups within molecules to yield ?
e.g. mutases, ? (methylmalonyl CoA mutase: methylmalonyl CoA to succinyl CoA)
Ligases: Join two molecules in an ? process and
Catalyze formation of bonds between carbon and ?, ? and ? coupled to hydrolysis of ? (get energy mainly from ATP) phosphates (pyruvate carboxylase: pyruvate -> oxaloacetate)
*imp!
Pepsin
substrate: protein
products: short polypeptides
Rennin
substrate: soluble casein (milk protein)
product: insoluble casein (curdled milk)*
MAJOR CLASSES OF ENZYME
- Oxidoreductases: catalyze reactions in which one molecule is oxidized while the other is reduced, transfer of electrons (e-) and hydrogens (H+)
e.g. of enzymes: oxidases, reductases, dehydrogenases, ?
(lactate dehydrogenase (NAD+ -> NADH + H) here COOH looses an electron and NAD gains an electron in the product side) - Transferases: transfer carbon, ? or ? groups
e.g. methyltransferases, ?, kinases, ? (serine hydroxymethyl transferase: serine -> glycine and CH2) - Hydrolases: enzymes that catalyze a hydrolytic cleavage reaction (use water to break a chemical bond) *most digestive enzymes are hydrolases as they (e.g. lipase) which need to reach the hydrophobic part of lipids need water around to break down the chemical bond
e.g. nucleases, proteases, phosphatases (urease: urea -> carbon di oxide and ammonia) - Lyases: catalyze the cleavage of C-C, C-S and C-N bonds
(catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure)
e.g. decarboxylases, aldolases, synthases, polymerases (e.g. pyruvate decarboxylate: pyruvate -> acetaldehyde) - Isomerases: catalyze the rearrangment of bonds within a single molecule, transfer of groups within molecules to yield isomeric forms
e.g. mutases, racemases (methylmalonyl CoA mutase: methylmalonyl CoA to succinyl CoA)
Ligases: Join two molecules in an energy-dependent process (usually from ATP) and
Catalyze formation of bonds between carbon and oxygen, sulfur and nitrogen coupled to hydrolysis of high energy phosphates (get energy mainly from ATP) phosphates (pyruvate carboxylase: pyruvate -> oxaloacetate)
note:
lyases = catalyze cleavage of C-C, C-S, C-N
ligases = join molecules between C-O, C-S, C-N
NOMENCLATURE
POTENTIALLY CONFUSING ENZYME NOMENCLATURE:
- Synthetase: ? ATP
- Synthase: ? ATP
- Phosphatase: ? phosphates
- Phosphorylase: ? phosphates (cleave bonds by ? - phosphorolysis)
- Dehydrogenase: catalyze ? reactions (i.e., transferring hydrogen to NAD+/NADPH+)
- Oxidase: ? is the acceptor of electrons or hydrogen, and oxygen atoms are not incorporated into ?
- Oxygenase: catalyze the incorporation of molecular O2 to a ?.
NOMENCLATURE
POTENTIALLY CONFUSING ENZYME NOMENCLATURE:
- Synthetase: ATP needed
- Synthase: no ATP needed
- Phosphatase: removes phosphates
- Phosphorylase: add phosphates (cleave bonds by orthophosphate - phosphorolysis)
- Dehydrogenase: catalyze oxidation/reduction reactions (i.e., transferring hydrogen to NAD+/NADPH+)
- Oxidase: oxygen is the acceptor of electrons or hydrogen, and oxygen atoms are not incorporated into substrate
- Oxygenase: catalyze the incorporation of molecular O2 to a substrate.
CLASSES OF ENZYMES
Polymerases: catalyze polymerization reactions such as the synthesis of ?
Proteases: break down proteins by ? bonds between ?
Kinases: Catalyze the addition of ? groups to molecules (protein kinases are very common in physiology)
?: Hydrolyze ATP (Na, K- ATPase)
Synthases: synthesize molecules in ? reactions by condensing two smaller molecules together with or w/o using ATP?
Phosphatase: catalyze the hydrolytic ? of a phosphate group from a molecule
PROPERTIES OF ENZYMES
- Active sites: enzymes contain a special
pocket called the ‘?’ which has a
high ?
AAs contain amino acid ? that
participate in substrate binding and catalysis
active sites are:
* “ ? ”
* Sensitive to ? changes
* ? by high heat
* Inhibited by ?
CLASSES OF ENZYMES
Polymerases: catalyze polymerization reactions such as the synthesis of dna and rna
Proteases: break down proteins by hydrolyzing bonds between AAs
Kinases: Catalyze the addition of phosphate groups to molecules (protein kinases are very common in physiology)
ATPase: Hydrolyze ATP (Na, K- ATPase)
Synthases: synthesize molecules in anabolic reactions by condensing two smaller molecules together w/o using ATP
Phosphatase: catalyze the hydrolytic removal of a phosphate group from a molecule
PROPERTIES OF ENZYMES
- Active sites: enzymes contain a special
pocket called the ‘active’ which has a
high specificity
AAs contain amino acid side chain that
participate in substrate binding and catalysis
active sites are:
* “ reusable ”
* Sensitive to pH changes
* denatured by high heat
* Inhibited by poison
PROPERTIES OF ENZYMES
Catalytic Efficiency: reactions catalyzed by enzymes are #? times faster than uncatalyzed reactions.
Specificity: enzymes interact with ALOT OR FEW substrates? and catalyze only one type of chemical reaction.
Presence of Cofactor and coenzymes:
- what does apoenzyme need for it to work?
- vitamin is analogous to ? in terms of function
*? and ? are often the metabolically active form of the vitamins.
PROPERTIES OF ENZYMES
Catalytic Efficiency: reactions catalyzed by enzymes are 103-108 times faster than uncatalyzed reactions.
Specificity: enzymes interact with one or v few substrates and catalyze only one type of chemical reaction.
Presence of Cofactor and coenzymes:
- what does apoenzyme need for it to work? = “cofactor” thus apoenzyme + cofactor = holoenzyme
- vitamin is analogous to cofactor in terms of function (enzymes in body need vitamins to produce e.g. holoenzyme)
*coenzymes and cosubstrates are often the metabolically active form of the vitamins.
PROPERTIES OF ENZYMES
Location in the cell: Many enzymes are in specific ? in the cell (?) and in specific ?
some reactions are isolated from others (avoiding ? for the substrate or enabling more favorable conditions, like ?)
Recall: protein sorting importance to maintain this ?.
e.g. cytosol: here glycolysis, PPP, FA synthesis;
mitochondria: TCA cycle, fatty acid oxidation, oxidation of pyruvate
nucleus: dna and rna synthesis
PROPERTIES OF ENZYMES
Location in the cell: Many enzymes are in specific organelles in the cell and in specific cells
some reactions are isolated from others (avoiding competition for the substrate or enabling more favorable conditions, like pH)
Recall: protein sorting is important to maintain compartmentalization.
e.g. cytosol: here glycolysis, PPP, FA synthesis;
mitochondria: TCA cycle, fatty acid oxidation, oxidation of pyruvate
nucleus: dna and rna synthesis
ENZYME KINETICS
The study of the ? that are catalyzed by ?.
Studying enzyme kinetics allows for the understanding of how each ? works.
o The enzyme’s ? mechanism
o The control of enzyme ?
o Its role in ?
o Possible inhibition by ?, agonists or antagonists
ENZYME KINETICS
The study of the chemical rxn that are catalyzed by enzymes
Studying enzyme kinetics allows for the understanding of how each enzyme works.
o The enzyme’s catalytic mechanism
o The control of enzyme activity
o Its role in metabolism
o Possible inhibition by drugs, agonists or antagonists
MICHAELIS-MENTEN KINECTS
The equation describes how ? varies with ? concentration -> single substrate enzyme kinetics!
An enzyme reversibly combines with its substrate to form an ? complex that yields a product P, releasing the free ?.
[in vitro = in glass (laboratory)
in vivo = in live animals]
Assumptions/conditions:
Relative concentration of enzyme and substrate
[S] > > [E] → % of total substrate bound by the enzyme at any one time is small
?: ES complex does not change with time. Rate [ES] formation = [ES] disassociation
? velocity (V0): reaction is measured as soon as enzyme and substrate are mixed.
Concentration of ? is very small. Rate of P -> ES can be ignored
Total enzyme concentration [E] does not change or changes over time?
Equation describes how reaction velocity varies with substrate concentration -> single substrate enzyme kinetics!
An enzyme reversibly combines with its substrate to form an ES complex that yields a product P, releasing the free enzyme.
Assumptions/conditions:
Relative concentration of enzyme and substrate
[S] > > [E] → % of total substrate bound by the enzyme at any one time is small
steady state: ES complex does not change with time. Rate [ES] formation = [ES] disassociation
initial velocity (V0): reaction is measured as soon as enzyme and substrate are mixed.
Concentration of P is very small. Rate of P -> ES can be ignored
Total enzyme concentration [E] does not change over time?
Km Michaelis-Menten constant is characteristic of an enzyme and its particular ? and reflects the ? of the enzyme for that ?.
Km is equal to the ? concentration at which the reaction velocity is ?
Km does not vary with ? concentration
Km Michaelis-Menten constant is characteristic of an enzyme and its particular substrate and reflects the affinity of the enzyme for that substrate.
Km is equal to the substrate concentration at which the reaction velocity is 1/2 Vmax
Km does not vary with enzyme concentration
Enzyme 1 has a high affinity for its substrate because a ? concentration of ? is needed to ?-saturate the enzyme
-> this is represented in the small Km
Enzyme 2 shows a ? affinity to the substrate -> represented in the large Km
Relationship of initial velocity to enzyme concentration:
→ rate of the reaction is directly proportional to the ? concentration at all substrate concentrations. (if 1⁄2 [E] → 1⁄2 ? and ?)
(if more enzymes added then initial velocity and max velocity can be increased and if enzymes reduced then less enzymes to react w substrate so velocity also goes down)
Order of reaction:
First order [ ? ] < < Km the velocity of the reaction is nearly proportional to the ? concentration.
(“linear curve” thus adding substrates then can increase velocity but not the case for zero order)
Zero order [ ? ] > > Km the velocity of the reaction is ? and equal to ?
-> rate of reaction is ? of substrate concentration
(reaching a plateau after Km)
Enzyme 1 has a high affinity for its substrate because a low concentration of substrate is needed to half-saturate the enzyme
-> this is represented in the small Km
Enzyme 2 shows a low affinity to the substrate -> represented in the large Km
Relationship of initial velocity to enzyme concentration:
→ rate of the reaction is directly proportional to the enzyme concentration at all substrate concentrations. (if 1⁄2 [E] → 1⁄2 Vo and Vmax)
(if more enzymes added then initial velocity and max velocity can be increased and if enzymes reduced then less enzymes to react w substrate so velocity also goes down)
Order of reaction:
First order [S] < < Km the velocity of the reaction is nearly proportional to the substrate concentration.
(“linear curve” thus adding substrates then can increase velocity but not the case for zero order)
Zero order [S] > > Km the velocity of the reaction is constant and equal to Vmax
-> rate of reaction is independent of substrate concentration
(reaching a plateau after Km)
Michaelis Menten kinetics show hyperbolic curve
(i.e.; myoglobin binding to O2 “single substrate”)
Allosteric enzymes do not show Michaelis-Menten kinetics; they show a ? curve (i.e.; hemoglobin binding to O2)
(myoglobin has higher affinity than hemoglobin if oxygen sat on y-axis and P O2 (oxygen affinity) on x-axis as myoglobin has higher affinity to O so harder for molecule to deliver oxygen to skeletal muscles so oxygen will unbind eaiser than haemoglobin)
Michaelis Menten kinetics show hyperbolic curve
(i.e.; myoglobin binding to O2 “single substrate”)
Allosteric enzymes do not show Michaelis-Menten kinetics; they show a sigmoidal curve (i.e.; hemoglobin binding to O2)
(myoglobin has higher affinity than hemoglobin - only has 1 subunit.
if oxygen sat on y-axis and P O2 (oxygen affinity) on x-axis as myoglobin has higher affinity to O so harder for molecule to deliver oxygen to skeletal muscles - only delivers it when the body is depried of O2; hemoglobin when 1 oxygen binds to one of its subunit its affinity for oxygen increases; beta reacts with alpha but not with beta).
THE LINEWEAVER-BURK PLOT
When Vo is plotted against [S], it is not always possible to determine when Vmax is achieved because of the ?.
(saturation of enzyme with substrate is known as ? )
Mathematically, the reciprocal 1/v0
and 1/[S] will be plotted to obtain a
straight line
* Calculation of Km and Vmax → enzyme ?
* It can also help to determine the mechanism of action of enzyme ?
(so we know the exact number on x and y so no need to use complicated math formulas)
THE LINEWEAVER-BURK PLOT
When Vo is plotted against [S], it is not always possible to determine when Vmax is achieved because of the hydperbolic curve.
(saturation of enzyme with substrate is known as Vmax)
Mathematically, the reciprocal 1/v0
and 1/[S] will be plotted to obtain a
straight line
* Calculation of Km (x) and Vmax (y) → enzyme activity
* It can also help to determine the mechanism of action of enzyme inhibitors
(so we know the exact number on x and y so no need to use complicated math formulas)
In vitro studies → information on how enzymes function in ? cells (in vivo)
Different enzymes show different responses to changes in
? concentration
?
?
Substrate concentration:
The rate of an enzyme-catalyzed reaction increases with the ? concentration until a maximal ? Vmax (μmol/min)
When (Vmax) is reached -> saturation (substrate bound to all available ? of enzymes)
Temperature:
* Reaction velocity ? with temperature until a ? is reached
* Increase is the result of increased number of molecules having sufficient energy to pass over the ? barrier
* Further elevation of the temperature results in a ? in reaction velocity due to denaturation of proteins
The optimal temperature for most mammalian enzymes is ? (95-104 °F)
!! fever dangerous as it ? protein’s enzyme hence no ? rxn, same for ? (cold temp. for enzymes) !!
In vitro studies → information on how enzymes function in ? cells (in vivo)
Different enzymes show different responses to changes in
substrate concentration
temp.
pH
Substrate concentration:
The rate of an enzyme-catalyzed reaction increases with the substrate concentration until a maximal velocity Vmax (μmol/min)
When (Vmax) is reached -> saturation (substrate bound to all available binding sites of enzymes)
Temperature:
* Reaction velocity increases with temperature until a peak is reached
* Increase is the result of increased number of molecules having sufficient energy to pass over the energy activation barrier
* Further elevation of the temperature results in a decrease in reaction velocity, denaturation of proteins
The optimal temperature for most mammalian enzymes is 35-40°C (95-104 °F)
fever dangerous as id denatures protein’s enzyme hence no biochemical rxn, same for hypothermia (cold temp. for enzymes)
pH:
* ? pH (concentration of H+) conditions can affect the ?
* The pH can affect the ? state of the ? site
- Extreme pH conditions can also ? enzymes (the structure of the catalytically active enzyme depends on the ionic character of the ?)
- pH ? of enzymes may vary (pepsin, trypsin, alkaline phosphatase)
pH:
* extreme pH (concentration of H+) conditions can affect the reaction veloctiy
* The pH can affect the ionization state of the active site (thus change ionization of amino acids and thus change properties of enzymes)
- Extreme pH conditions can also denature enzymes (the structure of the catalytically active enzyme depends on the ionic character of the amino acid side chains)
- pH optimum of enzymes may vary (pepsin, trypsin, alkaline phosphatase)
INHIBITION OF ENZYME ACTIVITY
Inhibitor: any substance that can diminish the ? of an enzyme-catalyzed reaction
- Irreversible (binds to covalent bonds; inactivate enzymes, e.g. lead -> ferrochelatase i.e., part of the synthesis of heme group)
(can also be called “suicidal” as it kills enzymes and itself; ferrochelatase is part of synthesis of heme groups so no heme group -> no oxygen transport thus fatal) - Reversible inhibitors bind to the enzyme through ? bonds
The ? of the enzyme-inhibitor complex leads to the separation of the reversibly
bound inhibitor, enzyme activity can be restored
Competitive inhibition
Noncompetitive inhibition
COMPETITIVE INHIBITOR
Binds ? to the ? that the substrate would normally bind, competing with substrate for that site.
- it intereferes with ? site of enzyme
INHIBITION OF ENZYME ACTIVITY
Inhibitor: any substance that can diminish the velocity of an enzyme-catalyzed reaction
* Irreversible (covalent bonds; inactivate enzymes, e.g. leadferrochelatase)
- Reversible inhibitors bind to the enzyme through non-covalent bonds
The dilution of the enzyme-inhibitor complex leads to the separation of the reversibly
bound inhibitor, enzyme activity can be restored
Competitive inhibition
Noncompetitive inhibition
COMPETITIVE INHIBITOR
Binds reversibly to the same site that the substrate would normally bind, competing with substrate for that site.
- it intereferes with active site of enzyme
- Effect on Vmax: inhibitor effect is ? by increasing [S]
High enough [S] → reaction velocity reaches the same Vmax observed in the absence of inhibitor - Effect on Km: competitive inhibitor ? for given substrate
competitive inhibitor reduces ? of E for S (competing!!) More substrate is needed to reach 1⁄2 Vmax - Effect on the Lineweaver-Burk plot
- 1/Vmax = changes or unchanged?
- 1/Km (think 1/Km = affinity) is ? in the presence of the competitive inhibitor
- Effect on Vmax: inhibitor effect is reversed by increasing [S]
High enough [S] → reaction velocity reaches the same Vmax observed in the absence of inhibitor - Effect on Km: competitive inhibitor increases Km for given substrate
competitive inhibitor reduces affinity of E for S (competing!!) More substrate is needed to reach 1⁄2 Vmax - Effect on the Lineweaver-Burk plot
- 1/Vmax = unchanged
- 1/Km (think 1/Km = affinity) is higher in the presence of the competitive inhibitor
