CHEM 4600: BIOCHEM TEST 2
27 Cards in this Set
| Front | Back |
|---|---|
|
oxidoreductase
|
enzyme that catalyzes oxi-reduc rxn using NAD+/FAD
eg: dehydrogenases
|
|
transferases
|
enzymes that catalyze transfer of functional groups
eg: transaminase,
transcarboxylase, hexokinase
|
|
Hydrolyases
|
enzymes that cleave bonds with the addition of water (ex: proteases: trypsin, thrombin, chymotrypsin) carboxypeptidase A
|
|
Lyases
|
Catalyze carbon-carbon bond and carbon-nitrogen bond cleavage
Release CO2 from a b-keto acid
Some are reversible
eg pyruvate decarboxlyase
|
|
Isomerase
|
An enzyme that rearranges the atom in a molecule.
change from one isomer to another, eg cis-trans isomerism
eg maleate--fumarate
|
|
ligase
|
enzyme that catalyzes joining of 2 large molecules by forming chemical bond
-couples 2 substrates w/ splitting of ATP
S + S + ATP---> S + ADP + P
|
|
enzyme catalysis
|
-protiens that enhance rxn rate by lowering EA
-E recognizes S & induces the TS
-E changes shape when S bound (tighter fit, chem groups into position to catalyze, creates fav cond)
-S held in active site by IMF
-E provides catalytic surface
-Enyzyme surface stabilizes the TS
-transf…
|
|
steady state theory
|
theory in enzyme kinetics
-the production = consumption of TS [ES] remains constant
-persists until almost all S is consumed
|
|
V(max)
|
hypothetical maximum rate: when all substrate is bound to enzyme
hypothetical because continuously binding and converting to product, then unbinding
|
|
Km
|
enzyme's "affinity" with substrate
-measure of [S] required for effective enzyme catalysis
-[S] @ 1/2 Vmax
-constant for a given enzyme
-small Km= tight binding, needs less S
-large Km=weak binding, needs more S to obt Vmax
|
|
Kcat
|
turnover #
-# S--P per E per unit of time
-1/sec
-measure of catalytic production under saturated Substrate(optimum conditions)
-with S excess K2=Kcat
|
|
Kcat/ Km
|
catalytic or enzyme efficiency
-measure of how perfect an E is
-apparent 2nd order rate constant
-large Kcat/ Km value= more P made per S per time
-measuers eff of transformation of bound P and eff of productive S binding
|
|
specific activity
|
measure of enzyme purity
-activity units/ protein
-mmole/min per mg
|
|
enzyme inhibitors
|
competitive
reversible, competes with S at active site
Km ↑ Vmax ∅
noncompetitive
irreversible, I binds to E or ES at diff site
Km Ø Vmax↓
uncompetitive
irreversible, I binds to ES at diff site, alters E structure to make I site available
Km↓ Vmax ↓
|
|
Ordered Sequential
|
Substrate binding order and product release order are constant
ex. Pyruvate >>> Lactate; NADH binds first, Lactate released first
|
|
double displacement
|
catalytic mechanism
one S binds 1 P released
ping pong mechanism
|
|
Catalytic residue
|
-alter pka of a residue or H20
-activate part of S
-stabilize TS
-in active site and weaken bondes
|
|
protease
|
an enzyme that cleaves peptide bonds via hydrolysis
-cleavage is slow due to resonance in bond
so enzyme must facilitate Nu attack at normally unreactive C=O
|
|
general acid-base catalysis
|
catalysis in which a protein is transferred in the transition state
|
|
chymotrypsin
|
pancreatic enzyme that cleaves on C-term side of AA WYFML
-covalent and AB catalysis
-Nu becomes briefly covalently attached
|
|
List the types of proteases.
|
Serine protease (OH), Aspartic protease (COO), cysteine protease (SH) and metalloproteases. (Zn)
|
|
isozymes
|
related proteins with similar but not identical catalytic activity
-eg LDH and H/M subunits
|
|
reversible covalent modification
|
a mechanism of enzyme regulation in which the enzyme's activity is either incr or decr by the reversible covalent addition of a group such as phosphate or AMP to the protein
-eg phosphorylation
|
|
Proteolytic Activation
|
Enzymes that cycle between active and inactive forms. Hydrolysis of peptide bonds in inactive enzymes produce active enzymes. Chymotrypsin, trypsin, and pepsin are all activated this way.
-irreversible converstion btw inactive (zymogen) to active enzyme
|
|
chymotrypsinogen
|
chymotrypsinogen (inactive) is activated by trypsin via proteolytic cleavage to form π chymotrypsin
-π chymo is cleaved by itself to make α chymo (3 chains)
α chymotypsin - A B C chains linked by disulfide bonds
|
|
cofactors
|
-any molecule (org or inorganic) that aids in catalysis, (protein fxn)
-two types
coenzyme : nonprotein org that aids in catalysis, binds with IMF
prosthetic group: nonprotein org molecule that aids, binds convalently (stuck)
enzyme + cofactor= haloenzyme
|
|
serine proteases
|
chymotrpysin: cuts WYFML
trypsin: cuts RK
elastase: cuts AG
all have catalytic triad
|
CHEM 4600: BIOCHEM TEST 2