The biosynthetic pathway of renin in mouse submandibular gland.

The present study set out to demonstrate the biosynthesis of a prorenin and its processing in the cell, using the richest known natural source of renin, the mouse submandibular gland. Cell-free translation of total poly(A+) RNA or mRNA selected using a renin cDNA yielded Mr = 45,000 preprorenin which in the presence of dog pancreatic microsomal membranes, was converted to Mr = 43,000 prorenin. The latter was seen during in vitro labeling of tissue with [35S]methionine. Prorenin was synthesized first and converted rapidly to Mr = 38,000 single chain renin. Renin was then hydrolyzed slowly to give two chains of Mr = 33,000 and 5,000 held together by disulfide bonds. The Mr = 38,000 and 33,000 species had similar peptide maps. Western blotting of fractions from a pepstatin affinity column identified the separation of prorenin from renin. The results suggested that both single and two-chain renin have an exposed active site. Testosterone stimulated synthesis of prorenin during in vitro labeling of female tissue. Thus, mouse renin is synthesized as a preprorenin (Mr = 45,000) which is converted to a prorenin (Mr = 43,000) and then to renin (Mr = 38,000) by rapid processing within the cell, after which renin is cut slowly to give a two-chain form.