Nonsuppressible insulin like activity of human serum. A potent inhibitor of insulin degradation

Abstract

Nonsuppressible insulin like activity soluble in acid ethanol (NSILA s) is a well characterized peptide derived from human serum which has previously been shown to have insulin like bioactivity and react with both insulin and NSILA s receptor sites in liver plasma membranes. In the present study we find that NSILA s is also a potent competitive inhibitor of the insulin degrading system of the liver plasma membrane. The most purified NSILA s preparation tested was 20 fold more potent than insulin itself, and significant inhibition of insulin degradation occurred at concentrations of NSILA s similar to those found in plasma.