Cofactors

Cofactors & Vitamins

Enzyme Cofactors

• Definition: Enzymes are proteins that may require additional components, known as cofactors, to be active.
• Types of Cofactors:
  • Metal Ions: Cations that include Cu²⁺, Zn²⁺, and Fe²⁺.
  • Coenzymes: Small organic molecules derived from vitamins that assist enzyme function.

Function of Coenzymes

• Role in Catalysis:
  • Coenzymes are crucial as they prepare the active site of the enzyme for catalytic action.
  • They bind to the enzyme, altering its shape to facilitate substrate binding and conversion to products.

Classification of Enzymes

• Simple Enzyme: Consists only of protein and is active without any cofactors.
• Enzyme with Cofactor: Requires a metal ion or coenzyme to be active.
  • Examples:
  • A. An enzyme that needs Mg²⁺ for phosphate ester hydrolysis.
  • B. An enzyme that requires Vitamin B3 for transferring acetyl groups.
  • C. Simple enzymes that are already active without cofactors.

Vitamins

• Definition: Organic compounds necessary for normal health and growth.
• Characteristics:
  • Needed in tiny (trace) amounts.
  • Must be acquired through diet as the body cannot synthesize them.
  • Divided into two main groups: Water-Soluble and Fat-Soluble.

Water-Soluble Vitamins

• Properties:
  • Must be consumed daily.
  • Highly soluble in water and cannot be stored in the body.
  • Excreted via urine and easily destroyed by heat, oxygen, or ultraviolet light.
• Common Types:
  • Thiamin (B1)
  • Riboflavin (B2)
  • Niacin (B3)
  • Pantothenic Acid (B5)
  • Pyridoxine (B6)
  • Cobalamin (B12)

Fat-Soluble Vitamins

• Properties:
  • Include Vitamins A, D, E, and K.
  • Soluble in lipids and not in water.
  • Serve critical roles in functions such as vision, bone health, antioxidant activity, and blood coagulation.
  • Stored in body tissues and not readily excreted in urine.
• Common Types:
  • Retinol (Vitamin A)
  • Cholecalciferol (Vitamin D)
  • Tocopherol (Vitamin E)
  • Menaquinone (Vitamin K)