enzyme regulation-lecture 17

pathway

• sequential steps in which the product of one reaction is the substrate for the next one

• a different enzyme catalyzes a different step of the reaction pathway

committed step

first step in reaction cascade that initiates the unique pathway

rate-limiting step

slowest step of the reaction and is irreversible

what is the first step of the pathway?

committed step

which step is irreversible?

rate-limiting step

what stage does the allosteric enzyme regulation catalyze?

in the committed stage

how are allosteric enzymes regulated?

by activators or inhibitors

where do allosteric enzymes bind at?

at allosteric sites non-covalently and changes the affinity

allosteric enzymes activators effects

decrease Km and no change on Vmax

allosteric enzymes inhibitors effects

increase Kmax or increase Kmax and decrease Vmax

covalent modification (phosphorylation/dephosphorylation)

regulation achieved by addition or deletion of phosphate group

how do you reverse covalent modification?

by removing phosphate group (dephosphorylation)

what other molecules can covalently modify?

acetyl, ADP-ribose, or lipid molecules

protein-protein interactions

acheived by direct interaction with other proteins in the cells (ex:g-protein)

proteolytic cleavage

undergoes cleavage during synthesis while others are stored or secreted proenzymes

what are proenzymes?

precursor (parent) proteins that undergo proteolytic cleavage to be activated

which conformational change is irreversible?

proteolytic cleavage

what is the relationship of the rate of reaction to amount of enzyme present?

proportional

the enzyme induction or repression is a ____ process

slow