Enzyme and Cofactor Classes Flashcards
Oxidoreductases
Aox + Bred Ared + Box
oxidase, hydroxylase: transfer O2 atoms to water or to substrate and water;
O2–> H20
dehydrogenase, peroxidase, reductase;
oxygenase (transfer both O2 atoms to substrate;
cytochrome p450
Common coenzymes of oxidoreductases
NADH, NADPH, FADH2
Transferase
AB+CA+BC
name: which chemical group is transferred or what chemical is synthesized
aminotransferase
transferase; transfers amine group (transaminase)
kinase
transfers a phosphate group
Synthase
indicates what kind of product is formed (glycogen synthase)
Hydrolase
Breaks a CX bond using water
X=O, N, S
protease, esterase, phosphatase, peptidase, urease
Lyase
Cleave C-C, C-O, C-S, and C-N bonds by means other than oxidation or hydrolysis;
decarboxylase, aldolase;
reverse reactions to form bonds: synthases; form C=C bonds by removing H2O from COH-CH
isomerase
no atoms lost or added, only rearranged;
epimerase, racemase, mutase
Ligase
Form C-C, C-S, C-O, C-N bonds and require ATP or another nucleotide;
synthetase (has T because it needs ATP)
6 classes of enzymes
oxidoreductases, hydrolase, lyase, ligase, isomerase, transferase
cofactors
vitamins, metal ions;
deficiency causes a range of diseases and without co-factor, respective chemical reaction cannot occur
ATP, ADP/Pi, AMP/PPi
carry phosphoryl groups
Very high energy bond stores chemical energy and leads to protein phosphorylation
NADH/NAD+
Shuttles electrons for redox of biological fuels, helps produce ATP
NADPH/NADP+
Shuttle electrons for oxidation in biosynthesis reactions
FADH2/FAD
FMNH2/FMN
Shuttle electrons for redox of biological fuels
more powerful than NAD’s: very strong oxidizing agents
Always bound to protein (prosthetic groups)
coenzyme A
carries acyl group O=C-R (R=CH3 and longer)
Biotin
Carries CO2 for carboxylation
Tetrahydrofolate
amino acid metabolism;
carries 1 carbon unit to carbon or sulfur
S-adenosylmethionine
carries methyl group to oxygen or nitrogen
Pyridoxal phosphate
cofactor/coenzyme that reacts with amines (NH2, NH) to catalyze amino acid metabolism, transamination reactions
Thiamine pyrophosphate
co-factor/co-enzyme that reacts with aldehydes/ketones to catalyze decarboxylation at the R group
Protease
part of hydrolase group
Cysteine proteases, aspartic proteases, metalloproteases, serine proteases
cysteine protease
active site requires cysteine residue;
papain, calpain, interleukin-1-b converting enzyme
aspartic protease
active site requires aspartate residue
ex. pepsin, rennin, HIV protease
active at low pH
rennin
aspartic protease;
inhibited by pepstatin and mimics protein substrate
HIV protease
(drug target because leads to mutation–cocktail)
metalloproteases
active site metal ion required
usually Zn2+, sometimes Co2+
ex. carboxypeptidase- release C terminal aa; thermolysin, collagenase, matrix metalloproteases;
inhibited by EDTA
Serine proteases
Conserved Asp, Ser, His catalytic triad required;
trypsin, chymotrypsin, enteropeptidase, elastase, thrombin;
inhibited by DFP and serpins
has specificity from other AA around active site
how do enzymes enhance rate of reaction
energy, concentration, orientation
energy
“strain” the reactant to look more like the transition state or product; bind more tightly to transition state than to reactants or products (lower energy); changes can be subtle
concentration
trap two reactants close to eachother
orientation
orient two reactants so that proper regions are juxtaposed; stereospecificity
