Proteolytic Degradation of Human Recombinant Proinsulin/insulin by Sera from Acute Pancreatitis Patients and Complete Inhibition by Eglin-C

Sera from patients of biliary, alcoholic, and idiopathic acute pancreatitis with severity scored from 1 to 5 based on the Ranson criteria were tested for proinsulin/insulin degrading activity. Proinsulin degrading activity by normal controls was 8 +/- 4% as compared with 22-78 +/- 17% with a mean of 45% by the patient sera. An order of magnitude increase of proinsulin degrading activity was accompanied by an order of magnitude increase of immunoreactive pancreatic cationic trypsin(ogen) and (pro)elastase-2 as determined by radioimmunoassay with day 1 sera. Proinsulin degrading activity also showed a negative correlation with the clinical time course and dropped to normal by 6 days after admission. The decrease of proinsulin degrading activity was concomitant with a decrease of serum immunoreactive pancreatic serine proteases. High-performance liquid chromatography analysis of the proteolysis products showed the appearance of insulin and smaller peptides with no proinsulin conversion intermediates. Ninety to ninety-eight percent of proinsulin degrading activity was inhibited by anti-alpha 2-macroglobulin (alpha 2-M) antiserum, or (Ac)Eglin-C(J141), and 52% by an elastase and chymotrypsin-specific inhibitor, MeOSuc-Ala-Ala-Pro-boroVal-pinacol. E64c, TLCK, alpha 1-protease inhibitor (alpha 1-PI), or Trasylol inhibited proinsulin degrading activity by 10-17%, and anti-cathepsin B antiserum by 9%. The observed proinsulin degrading activity did not correlate with the Ranson's scores, age, sex, etiology, total serum immunoreactive insulin, calcium, albumin or alpha 2-M but had a negative correlation with serum alpha 1-PI (r = -0.55) and a positive correlation with serum esterase activity (r = .62).(ABSTRACT TRUNCATED AT 250 WORDS)