MCB Lec 11

product of one enzyme is often the substrate of the next enzyme, helps channel substrates into the enzymes , rate of cell metabolism increases

allows intermedietes to move efficently through active sites, some enzymes have multiple active sites and either lose or gain NH3

dissociates slowly from target enzyme

binds via noncolvalent
does not perfrom chemical changes
is reversible

- mimics the structure of substrate and
- competes w substrate for the same binding site
- only binds to free enzyme
- Km increases | Vmax unaffected

- binds to a site distinct from the active site
- binding distorts the active site conformation, impairing catalysis
- Km unaffected | Vmax reduced

only binds to ES complex
- Km reduces | Vmax reduced

proteins that can adopt two or more structures when a ligand binds
- have two or more distinct binding sites
- ligand binding at one site cause shift one conformation

displays sigmoidal kinetics

ligand binding to one subunit can affect the properties of an adjacent subunit by changing its conformation

most cells Low Km
Phosphorylate glucose for glycolysis

liver high Km
Phosphorylate glucose for glycogen synthesis

effects of substrate on allosteric enzymes

effects of non substrate molecules on allosteric transition

Serine, cystine, aspartyl, and metalloproteases

Using serine residue as a nucleophile
– Typically contains a catalytic triad: Ser-His-Asp

Using cysteine residue as a nucleophile
– Typically contains a catalytic dyad: Cys-His

Using a pair of aspartate residues to activate water as a nucleophile

Using metal ion (Zn2+) to activate water as a nucleophile

Large non-polar or aromatic side chains

long positive side chains
- lys, arg

Smaller side chains

by specific cleavage of a single peptide bond

enteropeptidase

pancreatic zymogens