Kallikrein and renin: molecular biology and biosynthesis

1. A cDNA clone library was constructed from male mouse submandibular gland poly(A)+RNA. 2. A 500 base-pair sequence consisting of a 3' untranslated region plus a 447 base-pair region coding for an amino acid sequence having 57% homology with the C-terminal 149 amino acids in the 230 amino acid chain of porcine pancreatic kallikrein was identified. 3. The sequence was strongly but not completely homologous with known mouse submandibular gland serine proteinase sequences and represents the first report of a DNA base sequence for a serine proteinase. It may be part of the gene coding for kallikrein. 4. The biosynthetic pathway for renin was established by continuous-labelling, pulse-chase and cell-free translation studies of submandibular gland tissue from normal and testosterone-induced mice. 5. Renin was synthesized as a mol. wt. 46000 preprorenin which is likely to be hydrolysed before completion of the nascent chain. A prorenin of mol. wt. 44500, pI 6.4 was identified and shown to be rapidly converted into a mol. wt. 40000, pI 6.2 renin, which was then converted more slowly into forms of mol. wt 35500, pI 5.6 and mol. wt. 34000, pI 5.4.