suffix for enzyme

example: transferase, transfer functional group to another molecule

3D surface complementary to substrate

binds substrate, forms enzyme-substrate complex (ES)

doesnt change rxn equilibrium, complex forms enzyme-product complex (EP)  

active, nonprotein component

apoenzyme is inactive

cofactors are metal (Zn, Fe)

small organic molecule

cosubstrate for transient association (NAD, CoA)

prosthetic groups also coenzymes but for permanent association (FAD,example)

all rxns have energy barrier that separates reactants/products

must have enough energy overcome barrier to transition state, enzyme allows rxn to happen fast with lower activation energy.

does NOT change rxn equilibrium

substrate concentration, temp, pH

max velocity (saturation; Vmax), reached with increased substrate concentration

example- body enzyme optimal at 37 degrees, increase above this will denature enzymes

affects ionization of active site (acid base H exchange)

pH optimum varies, pepsin for example is pH 2

assumes steady state, Vo, ES-complex

Km is affinity of enzyme for substrate, which is 1/2 Vmax

large Km is low affinity for substrate.

small Km s high affinity of enzyme for substrate

converts to linear curve, not hyperbolic like MM eqn.

estimates exact Vmax, determine mechanism of action of enzyme inhibitors

increases apparent Km for substrate, Vmax is still unchanged though.

therefore decreasing enzyme affinity for substrate

reduce cholesterol synthesase.

binds at active site of HM CoA reductase, to compete with HMG-CoA (which usually binds to form cholesterol)

antagonist bound irreversible, binds at diff site to inhibit enzyme in noncompetitive way. No way to fight this

decreases Vmax, Km unchanged. competitive will change Km (not Vmax cause it can be beat)

Alanine Aminotransferase

(ALT)

in plasma, signals possible damage to hepatic tissue

(enzyme in clinical dx)

dx of myocardial infarction

myocardial cell die (enzyme in clinical dx again)