Guinea Pig Insulin

Abstract

Abstract A method is described for the preparation of homogeneous insulin from the pancreatic tissue of the guinea pig. The amino acid composition of this insulin and of the separated S-sulfonated chains demonstrated that the primary structure of the molecule was intact. Guinea pig insulin sedimented as a monomer in analytical ultracentrifugation, even in the presence of equimolar zinc ion. Ultraviolet absorbance difference spectrophotometry showed that certain hydrogen bonds which may be involved in stabilizing the monomer, and possibly the hexameric aggregate, in crystalline bovine or porcine insulin may not exist in guinea pig insulin. The reason for the failure of guinea pig insulin to dimerize may be related to the replacement of the B-22 arginine by aspartic acid.