Jenny - enzyme2 Flashcards
covalent modification in small molecule
phosphrylation, acetylation, glycosylation
covalent modification in large
adp-ribosylation, glutathionylation, ubiquitination
allosteric regulation is what kind?
and how is regulated?
non-covalent
at least one site, separate from active site, where an allosteric activator or inhibitor can bind/alter enzyme shape and thus function
PFK-1 is sigmoidal (S-shaped) Vo vs. [S] curve. this is due to what?
cooperativity of S binding
when regulator subunit binds regulating molecule, what happen?
it induces change in shape, changing apparent Km and shows a sigmoidal relationship when binding is measured over different [S] => cooperativity
interconvertible enzymes are controlled by what?
covalent modification
converter enzymes catalyze what?
covalent modification
product of one reaction trasnferred directly to active site of next enzyme without diffusing into the solvent
metabolite channeling
different enzymes catalyzing reactions in the same pathway are bound together
multienzyme complex
different activities exist on a single, multifunctional (multidomain**) polypeptide chain
multifunctional enzyme
nucelophilic species are …?
electron rich
electrophilic species are ….?
electron poor
formation of what intermediate is characteristics of nucleophilic substitution?
tetrahedral intermediate
direct displacement in nucleophihc subsitition has what?
transition state
in cleavage reaction, enzymes do waht?
enzymes can modify substrates to temporarily generate unstable forms (C-, C+. O- etc) more susceptible to reactions
oxidizing agent
gains electron (is reduced)
reducing agent
donates electrons (is oxidized)
in acid-base catalysis, general base(B:) can act as ___
proton acceptor
in acid-base catalysis, general acid (BH:) can ____
donate protons
in covalent catalysis, all or part of a substrate is bound covalently to the enzyme to form _____
reactive intermediate
under physiological conditions, the encounter frequency is about ?
10^8 to 10^9 M-1s-1
sucrose phosphorylase exhibits what?
covalent catalysis
glucose is transferred to enzyme then is donated to phosphate later
Km is measure of what?
affinity of E for S
Kcat?
Vmax/Etotal
normalize for enzyme concentration
=catalytic constant or turnover # enzyme
Kcat/Km
ratio describes “catalytic efficiency”
also normalized for Km
what is it that called “apparent second order rate constant” for the enzyme ( how well it works when substrate is not saturating)
Kcat/Km = catalytic efficiency
which enzyme of ubiquitin has catalytic cysteine?
E1
E1 forms what kind of bond between the Cys-SH and the COOH on the carboxyl terminal of uniquitin?
thioester bond
UBE3A encoding E3 dysfunction - servere neurological/motor problems. what syndrome?
angelman syndrome
VHL tumor supressor also and E3 ligase
what syndrome?
von hipel-lindau syndrome
epithelial Na channel loses its ubiquitin-based regulation -> early onset hypertension
what syndrome?
Liddle’s Syndrome
inactive enzyme precursor
zymogens
binding forces for catalysis (5)
- charge-charge interaction
- H bond
- hydrophobic interaction
- van der waals forces
- active site cysteine
example of active site cysteine utilizing catalysis
ubiquitin-conjugating enzymes
this is identified by covalent DFP labeling
ser-195
this is identified by affinity labeling with TosPheCH2Cl
His-57
this is identified by x-ray crystallography. The catalytic triad’
Asp-102
essential ions?
mostly metal ions
coenzymes (what kind of compound?)
organic compoud
apoenzyme has what
protein only and inactive
holoenzyme has what
cofactor with protein “active”
larger mobile metabolic groups can be attached at ____ of the coenzyme.
reactive center
many enzymes require ____
inorganic cations
this enzyme has an absolute requirement or are stimulated by metal ions. (K+, Ca2+, Mg2+)
metal-activated enzymes
this contains firmly bound metal ions at the enzyme active sites (ex. iron, zinc, copper, cobalt)
metalloenzymes
this enzyme is in mammal and synthesized from common metabolites
metabolite coenzymes
in mammal, this enzyme is derivatives of vitamins
vitamin-derived coenzymes
two classes of coenzymes
cosubstrates (altered/regenerated) prosthetic groups (remain bound, covalently bound to enzyme)
net reaction for dehydrogenases
NAD(P)+ 2e- + 2H+ -> NAD(P)H + H+
Iron in metalloenzymes , equation
Fe3+ + e- (reduced substrate) -> Fe2+ +(oxidized substrate)
Iron-sulfur clutsers can accept how many e- in a reaction?
1
