Proinsulin heterogeneity in pigs

: The isolation and characterization of a genetic variant of porcine proinsulin is described. The variant (II) differs from the known structure of porcine proinsulin (I) by a deletion of alanine C-39 (the 7th residue of the C-peptide). The two porcine proinsulins could only be separated by high resolution reversed phase HPLC. The ratio of proinsulin I to proinsulin II was found to be approximately 4:1 in 5 samples of porcine proinsulin prepared since 1969 and representing more than one million pancreata. Similarly, the two bovine proinsulins recently isolated from American cattle were found in a ratio of 7:1 in 3 proinsulin samples representing more than half a million ox pancreata. These results give a strong indication of duplication of the insulin gene in mammals.