ENZYMOLOGY Flashcards
Biologic proteins that catalyze biochemical reactions
ENZYME
Enzymes are _________ proteins, produced by living cells
INTRACELLULAR
Enzymes affect the ________ or speed of a chemical rxn;
__________ its chemical reaction
VELOCITY, speeding up
In an enzymatic process, enzymes are not _______ , ________, ________ nor ________ in composition; it only affects the speed
consumed, modified, altered, changed
Enzyme action is specific with ________ substrates
ORGANIC
In the lab, enzymes are measured in terms of their ________ and not in their __________
ACTIVITY, absolute values (concentration)
Activity of enzyme to a substrate is _________ with its concentration
directly proportional
Greater Enzymatic Activity =
High Enzyme Concentration
in serum, enzyme concentration is normally low, if it is high, it is indicative of:
a. Cellular Injury/ Damage
b. Increase Membrane Permeability
Hastens respiration process
Hydration of CO2
(Carbonic Acid = buffers the pH)
Transmission of nerve impulses
Nerve Induction
Helps in movement & heat generation
Muscle Contraction
Digestive juices contain enzymes to facilitate the interconversion of complex molecules in the diet. Absorption of macromolecules in the small intestine
Nutrient Degradation/ Digestion
Assist in growth & metabolism of a person
Growth & Reproduction
Conversion of energy stores (in ADIPOSE)
Energy Storage & Use
(Creatine Phosphate = ATP for muscles)
Components of an Enzyme
- ACTIVE SITE
- ALLOSTERIC SITE
A waterless cavity of an enzyme where substrates bind and undergo chemical reaction
ACTIVE SITE
Binding site for SUBSTRATE
ACTIVE SITE
Specific substrate can only bind to the active site of the enzyme
Enzyme-Substrate Specificity
A waterless cavity other than the active site that binds regulatory or effector molecules.
ALLOSTERIC SITE
Activators of Enzymes
1- Substrate (lab)
2- Cofactor (in the body)
Substances acted upon by enzymes
SUBSTRATES
Nonprotein substances added in the enzyme substrate complex to manifest an enzyme activity (to allow enzyme reaction)
COFACTORS
To ENHANCE enzymatic activity
COFACTORS
Organic cofactor that hastens enzymatic reactions
COENZYME (2nd Substrate)
COENZYME examples
NAD & NADP
Facilitates enzyme-substrate binding by altering the spatial configuration of the enzyme active site
ACTIVATOR
ACTIVATOR EXAMPLES
- Metallic Type: Mg, Ca, Fe, Zn, Mn
- Non-metallic Type: Cl, Br
Enzymes with similar enzymatic activity/ reaction but differ in their physical, biochemical, and immunologic characteristics
ISOENZYME
One way of differentiating/ fractionating isoenzymes is with the use of _____________
electrophoresis.
In the lab, ___________ is more preferred than _________ measurement due to its _______ to target tissue
isoenzyme measurement, total enzyme activity, HIGH SPECIFICITY
ISOENZYME EXAMPLES
- Creatine Kinase (CK1, CK2, CK3)
- Lactate Dehydrogenase (LDH1 to LDH5)
Protein portion of the enzyme
APOENZYME (Inactive Enzyme)
If the apoenzyme is subjected to _________, enzyme activity is lost
denaturation
Denaturation promotes at ________, would promote destruction of ____________
56degC, tertiary proteins
When an apoenzyme is tightly bound/attached with a coenzyme, it is termed as a _____________
prosthetic group
An active substance formed by the combination of a coenzyme and an apoenzyme (the product)
HOLOENZYME (Active Enzyme)
The naming of enzymes and its classifications was recommended by the
Enzyme Commission or the International Union of Biochemistry
The LONGER name
Defines the substrate acted on, or the reaction catalyzed, and possibly the coenzyme involved
Systematic Name
The usable/ trivial name of the enzyme
Frequently used name
Recommended Name
Always starts with E.C. followed by the 4 digits
1st – class of enzyme
2nd – subclass of enzyme
3rd – sub-subclass of enzyme
4th – serial number specific to enzyme sub-subclass
EC (Enzyme Commission) Numerical Code
Always starts with E.C. followed by the 4 digits
1st –
2nd –
3rd –
4th –
EC (Enzyme Commission) Numerical Code
1st – class of enzyme
2nd – subclass of enzyme
3rd – sub-subclass of enzyme
4th – serial number specific to enzyme sub-subclass
6 1st DIGIT CLASSIFICATION OF ENZYME
- Oxidoreductases
- Transferases
- Hydrolases
- Lyases
- Isomerases
- Ligases
Catalyzes the reduction oxidation reaction between 2 substrates; loss or gain of electrons; these enzymes utilize NAD/ NADP coenzymes (redox reaction)
Oxidoreductases
A– + B → A + B–
Oxidoreductases
In Oxidoreductases, ___ is the commonly transferred atom
H+
The conversion of the coenzymes NAD and NADP is catalyzed by _______
oxidoreductase
Catalyzes the transfer of a chemical group such as phosphate, methyl, among others (other than hydrogen) between two substrates
Transferases
A-X + B → A + B-X
Transferases
Transferases examples
1.AST/ SGOT (aspartate serum transferase)
2.ALT/ SGPT (alanine aminotransferase)
3.Gamma-glutamyl transferase (GGT)
Dehydrogenase examples
- Lactate Dehydrogenase (LDH)
- Glucose-6 Phosphate Dehydrogenase (G-6-PD)
Kinases example/s
Creatine Kinase (CK)
- Transfers PHOSPHATE groups
A–B + H2O → A–OH + B–H
Hydrolases
Hydrolysis of ether and ester & various bonds
Hydrolases
In the presence of water, hydrolases can _______ on different chemical bonds; when water is introduced, the bond is _______ (separates substrate A from substrate B).
cleave, cleaved
There must always be _____ for hydrolases to function
water
targets glycosidic bond connecting complex sugars
.Amylase
fats
Lipase
organic phosphomonoester bond
Phosphatase
6 Hydrolases examples
- Amylase
- Lipase
- Phosphatase
- Cholinesterase
- 5-nucleotidase
- ACE (acetyl cholinesterase)
ATP → cAMP + PPi
Lyases
Removal of groups from substrate without hydrolysis/ presence of water. The product remains having double bonds
Lyases
cAMP
PPi
cAMP - Cyclic Adenosine Monophosphate
PPi - Intermediate Diphosphate
Lyases example/s
1.Glutamate Decarboxylase Aldolases
2. Fructose biphosphate aldolase (ALS)
enzyme
that acts on carbohydrates
Fructose biphosphate aldolase (ALS)
A → B
Isomerases
The interconversion of geometric, optical, and positional isomers.
Isomerases
It would catalyze the interconversion of substrate A to become substrate B
Isomerases
Ab + C → A–C + b
Ligases
Joining of two substrate molecules coupled with the breaking of pyrophosphate bond in ATP
Ligases
Enzymes catalyze physiologic reactions by __________ that the reactants must reach
lowering the activation energy level
energy required for chemical reactions to proceed; important for product formation
ACTIVATION ENERGY
The _________ the activation energy required, the ________ the product formation
higher/greater
The _________ the activation energy required, the ________ the product formation
higher/greater, longer
The _______ the activation energy required, the ______ the product formation (in presence of enzymes)
lower, faster
The enzyme reaction is always _______ with the substrate.
reversible
Enzymes combined with only one substrate and catalyzes only one corresponding reaction
Absolute Specificity
Enzymes combined with all substrates containing a particular chemical group
Group Specificity
Enzymes attached to substrates with specific chemical bonds
Bond Specificity
Enzymes combine with only one specific optical isomer
Stereoisometric Specificity
Higher Substrate =
More Enzymatic Reaction
Enzyme is greater than substrate
FIRST ORDER KINETICS (E > S)
Reaction rate is proportional to substrate conc.
FIRST ORDER KINETICS (E > S)
Rate depends on concentration of substrate
FIRST ORDER KINETICS (E > S)
when substrate conc. reaches the maximal value, addition of more substrate could no longer increase the rate of reaction as enzymes are already exhausted
Saturation Kinetics
Only a fixed/ constant number of substrate (in excess) is converted to product per second
ZERO ORDER KINETICS (S > E) → used in the lab
In enzymatic reaction, we prefer that substrate is GREATER than enzyme → as long as substrate is in excess, there will be enzyme activity
ZERO ORDER KINETICS (S > E) → used in the lab
If the enzyme activity or concentration is __________, it cannot be measured by the machine, thus, it must be _________ → retest
too HIGH, serially diluted
lowers the conc. of enzyme
SERIAL DILUTION
Reporting of diluted serum
result of diluted serum is not reported, rather multiply the dilution factor to diluted serum
Higher Enzyme Concentration = More Substrate Binding = Faster Reaction
Enzyme Concentration
Velocity of reaction is proportional to enzyme as long as there is zero order kinetics
Enzyme Concentration
Normal except G-6-PD
LOW enzyme conc
HIGH enzyme conc.
Clinically Significant
Most physiologic reactions occur between a pH range of ________
7.0-8.0 (close to plasma pH of 7.35-7.45)
If the pH is too high or too low (extreme pH), enzymes are usually __________ , because enzymes are __________.
denatured/ inactivated, ergo proteins which undergo denaturation when pH is too acidic or too basic
can survive in extremely low and extremely high pH levels respectively
Acid phosphatase (pH 3-5) and Alkaline phosphatase (pH 9-10)
Tests for enzymes are done at __________ to mimic the ________ happening in the body.
body temp. 37°C, in vivo reaction
Assay temperature should be constant within ____ in which the enzyme is active at ____ , ____, and ____.
±0.1, 25°C, 30°C, 37°C
2 Temperatures for Enzymatic Testing:
- Room Temperature (25°C) – longer incubation
- Warm/ Body Temperature (37°C) – shorter; optimum temperature
Increased Temp.. =
Increased Rate of Chemical Rxn
Q10
(Temp. Coefficient) = Increased incubation temperature by _____ will have a characteristic of ______ in enzyme activity
10°C, twofold increase
Extreme Temp. =
Decreased Enzyme Activity
When the temp. exceeds 37°C, the activity starts to _____; which is _____
decrease, irreversible
significant decrease in enzyme activity (denaturation of tertiary structure)
40-50°C
significant decrease in enzyme activity (denaturation of tertiary structure)
40-50°C
significant denaturation/ inactivation
56°C
proteins are completely inactivated
60-65°C
Most enzymes are THERMOLABILE (inactive at high temperatures) except
The placental type of Alkaline phosphatase (Regan Alkaphose) which is thermoresistant/
thermostable
At low/ cold temperatures, enzymes are _______ ; but are preserved and become activated when temperature is ________
reversibly inactive, increased to room/ body temp
Non protein that enhances the reaction
Cofactors
It must be present in excess
Cofactors
when added to the enzyme structure could alter spatial configuration of the enzyme for proper substrate binding
Inorganic/ Activators
serves as 2nd substrate for enzymatic reaction (NAD). When coenzymes are increased, the velocity of the enzyme activity could also increase
Organic/ Coenzyme (prosthetic groups):
Agents that could interfere with the enzyme-substrate reaction
Inhibitors
competes with the substrate on the active site of the enzyme (alters/ slows down velocity by preventing enzyme binding)
Competitive Inhibitors
it binds on the site (allosteric site) other than the active site
Non-competitive Inhibitors
binds to enzyme-substrate (ES) complex
Uncompetitive Inhibitors
Increased Inhibitors =
Decreased Enzymatic Activity
Storage for substrates & coenzymes (reagents)
2-8degC [refrigerated]
Storage for storage of LDH (LD4 and LD5 are cold labile)
Room temp. (20-24 degC)
Storage for longer preservation of enzyme found in samples (serum)
-20degC or colder [freezer]
Why is thawing of frozen serum is only done for one time?
Multiple freeze thawing = can destroy enzyme
(denaturation) = falsely decreased
Factors that Influence Enzymatic Reactions
- Substrate Concentration
- Enzyme Concentration
- pH
- Temperature
- Cofactors
- Inhibitors
- Storage
- Interferences
It is the energy required to raise all molecules to the transition state in a chemical reaction so that products may be formed
Activation Energy
Increase in product concentration
= ↑ Rate of Substrate Conversion = ↑ Enzyme Concentration
Decrease in substrate concentration
= ↑ Products formed = ↓ Substrate Concentration
Decrease in coenzyme concentration (NADH)
Oxidized NAD (decreased) → reduced NADH (increased absorbance)
Always performed in zero-order kinetics (w/ fixed substrate)
Catalytic Activity
Performed during the linear phase of reaction
Measurement of Catalytic Activity
Simple outright procedure (only 1 measurement)
Fixed Time/Two-Point Assay
The reagents are combined, the reaction proceeds, the reaction is stopped and the amount of reaction is measured
Fixed Time/Two-Point Assay
Multiple enzyme activity is included in the procedure
Continuous Monitoring/ Kinetic Assays
Multiple measurements at specific time intervals or continuous measurement as absorbance changes.
Continuous Monitoring/ Kinetic Assays
Deviation from zero kinetics can be observed
Continuous Monitoring/ Kinetic Assays
30-60s interval; then absorbance is noted
Continuous Monitoring/ Kinetic Assays
2 Types of Enzymes Involved in Continuous Monitoring/ Kinetic Assays
- Primary Enzyme
- Secondary/ Coupling/ Indicator Enzyme
target enzyme in serum
Primary Enzyme
rely on primary enzyme activity for the reaction to proceed
Secondary/ Coupling/ Indicator Enzyme
An expression of the relationship between the velocity of the enzymatic reaction and the substrate concentration.
Michaelis-Menten Equation
The amount of enzyme that will catalyze the reaction of 1 μmol of substrate per minute (umol/ min)
IU; International Unit (EC) - [μmol/min]
Used by the Enzyme Commission
IU; International Unit (EC) - [μmol/min]
The amount of enzyme that will catalyze the reaction of 1 mol of substrate per second (mol/s)
Kat; Katal (SI) – [mol/s]
Used by the Système international
Kat; Katal (SI) – [mol/s]
The actual enzyme concentration
Enzyme Mass
Enzyme mass can be quantified using _______; enzymes are proteins with charged differences depending on the ___ and the isoelectric point
electrophoresis, pH, isoelectric point
2 enzyme theories
- Emil Fisher’s/ Lock & Key Theory
- Kochland’s Induced Fit Theory
Based on the substrate binding to the active site of the enzyme
Kochland’s Induced Fit Theory
The shape of the key (the substrate) must fit into the lock (the active site of the enzyme)
Emil Fisher’s/ Lock & Key Theory