5 - Regulation of the enzyme activity. Regulation by altering the absolute amount of the enzyme. Regulation by altering the activity of the enzyme – proenzymes, reversible covalent modification, allosteric regulation, etc.

sections

• regulation of enzyme activity

• allosteric enzymes

• inhibitors

• types of inhibitors

• activators of enzyme reactions

• regulation of enzyme activity

• Metabolic processes are coordinated by:

  • Allosteric effectors – bind away from the active site to increase or decrease enzyme activity.

  • Covalent modification – chemical groups (e.g., phosphate) are added/removed to switch enzymes on or off.

• allosteric enzymes

• regulated by effectors that covalently binds to areas other than the active site

• can alter affinity of enzyme to substrate

• 2 types:

  • - ve effectors inhibit

  • + ve effectors increases enzyme activity

• inhibitors

Enzyme Inhibition Summary:

• Irreversible Inhibitors:

  • Cause covalent modification of the enzyme

  • Decrease active enzyme concentration → ↓ ES complex

  • Often toxic or poisonous

  • Effects not easily reversed

• Reversible Inhibitors:

  • Competitive: Bind active site, compete with substrate, reversible by adding substrate

  • Non-competitive: Bind elsewhere, not reversed by substrate, ↓ Vmax, Km unchanged

  • Uncompetitive: Bind only to ES complex, ↓ both Vmax and Km

• types of inhibitors

• activators of enzyme reactions

• Fe ²⁺

• Mg ²⁺→ kinases

• Anions → Cl^- → salivary amylase activator