Acid-activation of rat prorenin following non-proteolytic alteration.

Abstract

Prorenin is an inactive precursor of renin (EC 3.4.23.15) which plays an important role in control of blood pressure and electrolyte balance. The inactive prorenin is irreversibly activated by trypsinization. The prorenin level in the plasma has been observed to be 5–10 times higher than that of renin (1–4). This fact has attracted the attention of many investigators. However, the mechanism of its activation or processing has not been clarified except for some reports on activation of human prorenin (2,5–7). It has been reported that human prorenin was activated by acidification as well as trypsinization (1,2,4–7). Recently we have observed that recombinant rat prorenin secreted from the Chinese hamster ovary cells transfected with a vector containing rat pre-prorenin cDNA (8) was also activated by dialysis at an acidic pH of 3.3 at 4°C (9). The amino acid sequence of rat prorenin prosegment, deduced from the cDNA (8), had a candidate scissile peptide bond for an autocatalytic activation by renin, a bond between L33 and L34. (Every amino acid residue for renin molecule was, in this paper, numbered from the N-terminal amino acid residue of pre-prorenin, Ml.) Therefore, there is the possibility that rat prorenin might be altered to an intermediate form by the autocatalysis during the acid treatment. In this study, we purified the recombinant rat prorenin to elucidate the biochemical properties of the acid-activated prorenin and to examine whether rat prorenin was auto-activated at acidic pH.