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Learning Objectives

• Identify core enzyme classes based on their functional descriptors.
• Distinguish between ATP-dependent and ATP-independent phosphate reactions.
• Recognize essential clinical cofactors required for specific enzyme functions.

1. Phosphate-Handling Enzymes

The movement of phosphate groups is a fundamental mechanism in signal transduction and metabolic regulation.

• Kinase: Catalyzes the transfer of a phosphate group from a high-energy molecule (usually ATP) to a substrate.
  • Example: Phosphofructokinase (PFK-1).
• Phosphorylase: Adds inorganic phosphate to a substrate without using ATP.
  • Example: Glycogen phosphorylase.
• Phosphatase: Removes a phosphate group from a substrate.
  • Example: Fructose-1,6-bisphosphatase 1.

2. Oxidation, Synthesis, and Relocation

Enzymes also manage the redox state and structural arrangement of molecules.

• Dehydrogenase: Catalyzes oxidation-reduction reactions.
  • Example: Pyruvate dehydrogenase.
• Carboxylase: Transfers carboxyl groups (−COOH). Often requires Biotin (B7).
  • Example: Pyruvate carboxylase.
• Mutase: Relocates a functional group within a molecule.
  • Example: Vitamin B12–dependent methylmalonyl-CoA mutase.

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