Purification and characterization of one-chain and two-chain renins from mouse submandibular gland

Biosynthetic processing of mouse submandibular gland renin involved sequential proteolytic cleavages of preprorenin to prorenin; the prorenin, in turn, rapidly converted to one-chain and slowly to two-chain renins that were both enzymatically active. One-chain and two-chain renins were purified by an eight-step purification including carboxymethyl cellulose and high performance liquid chromatography (HPLC). The specific activity of the purified one-chain renin was fivefold higher than the two-chain renin. Purified heavy-chain renin was obtained by dithiotreitol incubation of two-chain renin. The heavy chain, isolated by HPLC, retained less than 4% of the activity of the native two-chain, indicating that light-chain renin is essential for enzymatic activity. Previous data indicate that both one-chain and two-chain renins are secreted. One-chain renin is immediately secreted into the media after synthesis, whereas two-chain renin is secreted later. These results suggest that renin may be secreted by two separate pathways--an early pathway from the golgi and another pathway from the secretory granules. Our data indicate that renin biosynthesis and secretion are complex and may be controlled at multiple points.