VPT 321: Veterinary Neuropharmacology (2+1) copy 1

SYNTHESIS AND METABOLISM OF KININS

• Kinins are produced in response to tissue damage.
• Tissue damage causes the activation of Hageman factor, which is involved in the clotting mechanism.
• Hageman factor converts plasma prekallikrien to plasma kallikrein. Kallikreins are enzymes, which break down kininogens (the precursors of kinins). There are 2 forms of kallikreins: Plasma kallikrein and Tissue kallikrein (found in the pancreas).
• Plasma kallikrein converts high molcular weight kininogen to bradykinin.
• Tissue kallikrein converts low molecular weight kininogen to kallidin.

The kininogens are liver derived alpha₂ globulins.

Metabolism of kinins

• Two types of enzymes metabolise kinins
• Aminopeptidases
• Carboxypeptidases
• Aminopeptidases: Converts kallidin to bradykinin
• Carboxypeptidase: There are two forms
  • Kininase I and
  • Kininase II (ACE)