Enzymes Flashcards
It is a compound usually a protein, that acts as a
catalyst for a biochemical reaction
Enzyme
Composed only of protein
Simple Enzyme
Has a non protein part in addition to a protein part.
Conjugated Enzyme
Protein of the conjugated enzyme
Apoenzyme
Non protein part of the conjugated enzyme
Cofactor
Biochemically active conjugated enzyme produced from an
apoenzyme and a cofactor
Holoenzyme
Serves as a cofactor in a conjugated enzyme
Coenzyme
Reactant in an enzyme catalyzed reaction.
Substrate
Requires a coenzyme that is oxidized or reduced as the
substrate is reduced or oxidized
Oxidoreductase
Catalyzes the transfer of a functional group from one
molecule to another
Transferase
Catalyzes the transfer of amino group from one molecule to another
Transaminase
Catalyzes the transfer of phosphate group from ATP to give ADP and
a phosphorylated product.
Kinases
Catalyzes the hydrolysis reaction and is the central to the process of digestion
Hydrolase
Catalyzes the addition of a group to a double bond or the
removal of a group to form a double bond in a manner
that does not involve hydrolysis or oxidation
Lyase
Catalyzes the isomerisation of a substrate in a reaction
converting it to a molecule isomeric with itself.
Isomerase
Catalyzes the bonding together of two molecules into
one with the participation of ATP.
Ligase
Small part of an enzyme’s structure that is actually
involved in catalysis.
Active Site
The intermediate reaction species that is formed when a
substrate binds to the active site of an enzyme.
Enzyme-Substrate Complex
Active site in the enzyme has the fixed, rigid
geometrical conformation.
Lock-and-Key Model
Enzyme’s active site is not rigid and static.
Induced-Fit Model
Extent to which an enzyme’s activity is restricted to a
specific substrate, a specific group of substrate, a
specific type of chemical bond, or a specific type of
chemical reaction.
Enzyme Specificity
Catalyze only one reaction
Absolute Specificity
Act only on molecules that have a specific functional
group, such a hydroxyl, amino or phosphate groups.
Group Specificity
A caboxylpeptidase is an example of what specificity?
Group Specificity
A Catalase is an enzyme of what specificity?
Absolute Specificity
Act on the particular type of bond, irrespective to the
rest of the molecular structure.
Linkage Specificity
Act on a particular isomer
Stereochemical Specificity
Measures the rate at which an enzyme converts
substrate to products in a biochemical reaction
Enzyme Activity
Factors that affect the enzyme activity are:
Temperature
pH
Substrate Concentration
Enzyme Concentration
Temperature at which an enzyme exhibits maximum activity
Optimum Temperature
the charge on acidic and basic amino acids located at the active site
depends on?
pH
What can affect substrate, causing either protonation or
deprotonation of groups on the substrate.
pH
Active in the stomach, functions best at pH 2.0
Pepsin
Operates in the small intestines, function best at pH 8.0
Trypsin
physiological pH ranges from?
7.0-7.5
True or False
Decreased concentration of substrate will obtain the
enzyme activity.
False
Number of substrate molecules transformed per minute by
one molecule of enzyme uunder optimum conditions of
temperature, pH and saturation.
Turnover Number
True or False
The greater the enzyme concentration, the lesser the
reaction rate.
False
A microbial enzyme active at a conditions that would inactivate
human enzymes as well as enzymes present in other types of
higher organisms
Extremozymes
Microorganisms that thrives in extreme environments
Extremophile
Microorganisms with optimal growth at pH levels of 3.0 or below
Acidophile
Microorganisms with optimal growth at pH levels of 9.0 or above
Alkaliphile
Microorganisms whose temperature between 80C and 122C are needed to thrive
Hyperthermophile
Substance that slows or stops the normal catalytic function of an enzyme by binding to it.
Enzyme Inhibitor
Molecule that sufficiently resembles an enzyme substrate in
shape and charge distribution that it can compete with the
substrate for occupancy of the enzymes active site
Competitive Enzyme Inhibitor
Molecule that decreases enzyme activity by binding to a site
on an enzyme other than the active site. Presence of this causes a change in the structure of the
enzyme sufficient to prevent the catalytic groups at the active
site from properly effecting their catalyzing action.
Non-competitive Enzyme Inhibitor
Molecule that inactivates enzyme by forming a strong
covalent bond to an amino acid side chain group at the
enzymes active site.
Do not have structures similar to that of the enzyme’s normal
substrate.
Irreversible Enzyme Inhibitor
True or False
A cell that continually produces large amount of
enzyme for which substrate concentration is always
high is wasting energy. The production of the
enzyme needs to be “ turned off”.
False, substrate concentration is always “very low”
True of False
A product of an enzyme Catalyzed reaction that is
present in plentiful amounts in a cell is a waste of
energy if the enzyme stopped catalyzing the
reaction that produces the product. The enzyme needs
to be turned off.
False, if the enzyme “continues to catalyze”
Substance that bind at the regulatory sites of allosteric
enzymes.
Regulators
The shape of the active site is changed such that it
can more readily accept substrate.
Positive Allosteric Regulators
Changes to the active site are such that substrate is
less readily accepted.
Negative Allosteric Regulators
A process in which activation or inhibition of the first
reaction in a reaction sequence is controlled by a
product of reaction sequence.
Feedback Control
Catalyzes the breaking of peptide bonds that maintain the
primary structure of protein.
Proteolytic Enzymes
Inactive precursor of a proteolytic enzyme.
Zymogens
Process in which enzyme activity is altered by
covalently modifying the structure of the enzyme
through attachment of a chemical group or removal of
a chemical group from a particular amino acid within
the enzyme structure.
Covalent Modification
Process of addition of the phosphate group to the
enzyme by protein kinases
Phosphorylation
Removal of the phosphate group from the enzyme by
phosphatases
Dephosphorylation
is an enzyme with two or more protein chains (quaternary
structure) and two kinds of binding sites (substrate and regulator).
Allosteric Enzyme
an enzyme involved in the breakdown of glycogen to glucose
Glycogen phosphorylase
catalyze removal
of the phosphate groups.
Phosphatases
An enzyme that which effect the addition of phosphate groups
Protein kinases
is a substance that kills bacteria or inhibits their growth.
Antibiotic
An inhibitor that decreases enzyme activity by binding to a site on the enzyme other
than the active site
Reversible noncompetitive inhibitor
An inhibitor that inactivates enzymes by forming a strong covalent bond at the enzyme
active site
Irreversible Inhibitor
An inhibitor that has a shape and charge distribution similar to that of the enzyme’s
normal substrate
Reversible competitive inhibitor
An inhibitor whose effect can be reduced by simply increasing the concentrate of
normal substrate present
Reversible competitive inhibitor
A molecule closely resembling the
substrate. Binds to the active site and
temporarily prevents substrates from
occupying it, thus blocking the reaction
Competitive Enzyme Inhibitor
A molecule that binds to a site on an enzyme that is not the active site. The normal substrate still occupies the active site but the enzyme cannot catalyze the reaction due to the presence of the inhibitor.
Noncompetitive Enzyme Inhibitor
A molecule that forms a covalent bond to
a part of the active site, permanently
preventing substrates from occupying it.
Irreversible Enzyme Inhibitor
The active site has a fixed geometric
shape. Only a substrate with a matching
shape can fit into it.
Lock-and-Key Model
The active site has a flexible shape that can change to accept a variety of related substrates. Enzymes vary in their degree of specificity for substrates.
Induced-Fit Model
Such specifi city means an enzyme will catalyze a particular
reaction for only one substrate. This most restrictive of all specifi cities is not
common. Urease is an enzyme with absolute specificity.
Absolute Specificity
Such specificity means an enzyme can distinguish between
stereoisomers. Chirality is inherent in an active site, because amino acids are chiral
compounds. L-Amino-acid oxidase will catalyze reactions of L-amino acids but not
of D-amino acids.
Stereochemical Specificity
Such specificity involves structurally similar compounds that have
the same functional groups. Carboxypeptidase is group-specifi c; it cleaves amino
acids, one at a time, from the carboxyl end of the peptide chain.
Group Specificity
Such specificity involves a particular type of bond, irrespective of
the structural features in the vicinity of the bond. Phosphatases hydrolyze phosphate–
ester bonds in all types of phosphate esters. Linkage specifi city is the most general of
the specifi cities considered.
Linkage Specificity
is the intermediate reaction species that is formed when a
substrate binds to the active site of an enzyme.
Enzyme-substrate complex
is the relatively small part of an enzyme’s structure that is actually involved in catalysis.
Active Site
introduction of double bond (oxidation)
by formal removal of two H atoms from
substrate, the H being accepted by a
coenzyme
Dehydrogenase
transfer of an amino group between
substrates
Transaminases
transfer of a phosphate group between
substrates
Kinases
hydrolysis of ester linkages in lipids
Lipase
hydrolysis of amide linkages in
proteins
Protease
hydrolysis of sugar–phosphate ester
bonds in nucleic acids
Nuclease
hydrolysis of glycosidic bonds in
carbohydrates
Carbohydrase
hydrolysis of phosphate–ester bonds
Phosphatase
removal of H2O from substrate
Dehydratase
removal of CO2 from substrate
Decarboxylase
removal of NH3 from substrate
Deaminase
addition of H2O to a substrate
Hydratase
conversion of D to L isomer, or vice
versa
Racemase
transfer of a functional group from
one position to another in the same
molecule
Mutase
formation of new bond between two
substrates, with participation of ATP
Synthetase
formation of new bond between a
substrate and CO2, with participation
of ATP
Carboxylase
an enzyme that catalyzes the formation of peptide
cross links between polysaccharide strands in bacterial cell walls.
Transpeptidase
is an organic compound, essential in small amounts for the proper
functioning of the human body, that must be obtained from dietary sources because the
body cannot synthesize it.
Vitamin
