[LEC] UNIT 2 Enzymology Flashcards
T or F: Enzymes are specific proteins that catalyze
biochemical reaction without altering the
equilibrium point of the reaction or being consumed
or changed in composition.
T
Enzymes are usually present in _______ concentrations
minute
Primary structure- This refers to the _____, ______, and _______ of
amino acids in the polypeptide chain. In order to
function properly, proteins must have the correct
sequence of amino acids.
number, type, sequence
Secondary structure refers to the commonly formed arrangements
stabilized by______ bonds between nearby amino
acids within the protein molecule.
hydrogen
refers to the overall shape of the protein
molecule.
Tertiary structure
Quaternary structure results from the
interaction of more than one protein molecule, or
protein subunits, referred to as_______, that
functions as a single unit.
multimer
T or F: Clinically significant enzymes are extracellular
proteins that, when cell damage occurs, leak into the
bloodstream, serving as biomarkers for tissue injury
or disease.
F
Intracellular
This is the substance acted upon by the enzyme
Substrate
A water free cavity, where the substrate interacts
with particular charged amino acid residues
Active site
A cavity other than the active site; binds the
regulator molecules
Allosteric site
Where do regulator molecules bind?
Allosteric site
T or F: Substrate + Enzyme = Enzyme-Substrate Complex reaction is reversible
T
These are enzymes with same function but exist in
different forms
Isoenzyme
These are forms of enzymes that were
post-transcriptionally modified.
Isoforms
These are non-CHON (non-protein) molecules
necessary for enzyme activity such as activators and
coenzymes.
Cofactors
Examples of coenzyme
NAD, Niacin, Vitamins
Examples of activators
M: Mg, Mn, Ca, Zn
NM: Br, Cl
The different forms of isoenzymes may differ in select physical properties, such as:
- Amino acid composition
- Electrophoretic ability
- solubility and resistance to inactivation
Isoenzyme elevated in AMI (acute myocardial
infarction)
CK-MB
Most abundant CK isoenzyme
CK-MM
Most anodic CK isoenzyme
CK-BB
This is a coenzyme bound tightly to the enzyme.
Prosthetic group
The enzyme portion that is activated by the
prosthetic group.
Apoenzyme
Prosthetic group + Apoenzyme
Holoenzyme
Inactive precursor of an enzyme
Zymogen / Proenzyme
adopted a classification system
in 1961, with the standards revised in 1972 and 1978.
Enzyme Commission of the International Union of Biochemistry
catalyze an oxidation–reduction reaction between
two substrates
Oxidoreductase
Examples of Oxidoreductase
GLD
LD
G6PD
catalyze the transfer of a group other than hydrogen from one substrate to another
Transferases
Examples of Transferases
AST
ALT
catalyze hydrolysis of various chemical bonds
Hydrolases
Catalyze removal of groups from substrates without
ALD-Aldolase
hydrolysis; the product contains double bonds
Lyases
Examples of Hydrolases
ALP
ACP
Example of Lyase
Aldolase
Catalyze the interconversion of geometric, optical, or positional isomers
Isomerases
Example of Isomerase
Triosephosphate isomerase
Catalyze the joining of two substrate molecules.
Coupled with breaking of the pyrophosphate bond in ATP
Ligases
Example of Ligase
GSH-S
Enzymes play a
crucial role in regulating the availability of______
hormones to target tissues
thyroid
T or F: Some chemical reactions will occur at a slow rate if
there is not enough kinetic energy to drive the
reaction to the formation of products (uncatalyzed
reaction).
T
T or F: There is already a product in the Transition State
F
Enzymes ______ the activation energy so that the
reaction will be faster
lower
Proponent of Lock and Key
Emil Fischer
Porponent of Induced-fit
Daniel Koshland
refers to the ability of an enzyme
to selectively bind to a particular substrate,
facilitating a specific biochemical reaction
Enzyme specificity
Types of E. specificity
Absolute
Group
Bond
Stereoisomeric
Factors affecting E Activity
SEPTIC
Substrate conc
Enzyme conc
pH
Temperature
Inhibitors
Cofactors
In a ___ degree increase in temp, there is also a
doubling of the reaction
10
Level of protein denaturation
40 - 50 C
Decreases enzyme activity
Inhibitors
At high substrate
concentrations,
enzyme activity
_______
because all
active sites are
saturated.
plateaus
the amount of substrate that will give us half the Vmax
Michaelis’ Constant (KM)
Hypercolic graph
Michaelis-Menten
Slope or Linear graph
Lineweaver-Burk
the maximum speed of reaction
Vmax
What is the effect of extremely high temperature
to enzyme activity?
Denaturation
A compound that shares some structural feature
found in the substrate will typically physically bind
to the same form of the enzyme that the substrate
binds, often in the active site of an enzyme, and compete with the substrate for a place in the active site.
Competitive Inhibitor
Enzymes may also be sensitive to the presence of
other compounds that are called noncompetitive
inhibitors.
Non-competitive Inhibitor
may be observed in which the inhibitor
binds only to the ES complex; increasing substrate
concentration results in more ES complexes to
which the inhibitor binds and, thereby, increases the
inhibition
Uncompetitive Inhibitor
Measurement of Enzyme Activity
Product formation ^^^
Substrate concentration vvv
Cofactor concentration vvv
Altered concentration ^^^
1 IU =
1 umol/ min
Single measurement at a specific time
Fixed time
a.k.a. Continuous monitoring assay
Kinetic Assay
This inhibitor will show same Vmax and increased
Km in the Limeweaver-Burk Plot. (increased to the
right)
Competitive Inhibitor
