Vitamin K, Prothrombin and γ-Carboxyglutamic Acid

Abstract

Blood coagulation is a series of enzymatic reactions that sequentially convert zymogens of proteolytic enzymes to the corresponding active forms. The reaction sequence, termed waterfall or cascade reaction, ultimately leads to thrombin generation from prothrombin, with subsequent conversion of fibrinogen to fibrin.¹ Four of the zymogens require vitamin K for normal biosynthesis, prothrombin (factor II), factor VII, factor IX and factor X. The active forms of these enzymes are serine endopeptidases phylogenetically closely related to pancreatic serine enzymes like trypsin but with a very narrow substrate specificity —i.e., active factor X cleaves only two peptide bonds in prothrombin. Activation of . . .