Role of Vitamin K in the Synthesis of Prothrombin

Publisher Website
Google Scholar
Abstract
By means of a cholecystnephrostomy, which brings about a complete drainage of bile through the kidney, severe vit. K deficiency was produced in dogs. By employing these animals for assaying vit. K potency, it was found that 7[mu]g. of natural vit. Kl/kg. of body wt. restored the prothrombin level to normal in 24 hrs. while 9[mu]g. accomplished the same in 4 hrs. Menadione (2-methyl-1,4-naphthoquinone) was far less effective and irrespective of the dose, brought the prothrombin level only to 40% of normal. It is postulated that vit. K acts as a prosthetic group combining with the apoenzyme (AE) to form the holoenzyme AEK, which is responsible for the synthesis of prothrombin. The labile factor is not diminished in severe vit. K deficiency. In conformity with previous observations, the Ca requirement for optimum prothrombin time is increased when the prothrombin becomes diminished.
Keywords