Enzyme Inhibition & Regulation

noncompetitive inhibitor

(aka allosteric) inhibitor binds at the site separate from the active site, changing configuration preventing substrate binding

competitive inhibitor

inhibitor resembles substrate, competes for binding site

uncompetitive inhibitor

inhibitor binds to the enzyme-substrate complex, not the active site, binds to already formed enzyme substrates

irreversible inhibition

covalent modification of enzyme rendering it inactive

allosteric regulation

substrate binding at the active site is affected by the binding of a molecule at a different site

positive: opens active site

negative: closes active site

feedback control

end product of a metabolic pathway binds to an earlier enzyme in the same sequence to slow down/stop its own further production

positive: product enhances activity of first enzyme

negative: product inhibits the first enzyme

covalent modification

addition of a phosphate group on tyrosine/scrine/threonind residue triggers a conformational change in the structure. Actives/deactives enzyme

zymogens

synthesized in an inactive form (aka proenzyme), which has a longer protein segment that must be removed before the enzyme is active

genetic control

control amount of enzyme available in cell