Quantitative polyacrylamide gel electrophoresis and specific activities of human somatotropin and its derivatives

A preparation of human pituitary somatotropin examined in quantitative polyacrylamide gel electrophoresis is conformationally compact. The derived molecular weight by quantitative electrophoresis is consistant with the known mass of the hormone and value obtained by other methods. A plasmin-modified somatotropin is more compact and shows full activity in immunoassay, and in lymphocyte binding and somatotropic assays, with enhanced lactogenic activity. The N-terminal 134-amino acid fragment and a hendekakaihekaton fragment exist in non-monomeric forms. The N-terminal fragment has immunologic and biologic activity, with greatest activity in the in vivo somatotropic assay. The hendekakaihekaton fragment exhibited only marginal activity. All preparations showed heterogeneity of charge in quantitative electrophoresis with discreet charge isomerism recognizable for the native and plasmin-modified preparations.