Localization of renal vitamin K-dependent gamma-glutamyl carboxylase to tubule cells.

The renal vitamin K-dependent gamma-glutamyl carboxylase was present in microsomes prepared from the renal cortex as well as the inner and outer medulla of several species. When glomeruli were isolated from either dog or rat renal cortex, microsomes prepared from these glomeruli were devoid of carboxylase activity. Proximal tubules were isolated from rabbit renal cortex; microsomes derived from these tubules had easily measurable carboxylase activity. The experiments demonstrate that the vitamin K-dependent gamma-glutamyl carboxylase is located in renal tubule cells. Since the enzyme is found not only in cortex but also inner and outer medulla, its distribution is not restricted to specific tubule segments.