A biologically active insulin analogue with modification in the A2 position. [2-Valine-A] sheep insulin

The synthesis and biological evaluation of [2-Valine-A] insulin ([Val2-A]insulin) is reported. In this insulin, the isoleucine residue in position A2, invariant in the majority of mammalian insulins, is substituted by valine. The same substitution, along with four others, occurs naturally in the insulin produced by the owl monkey. Owl monkey insulin exhibits ca. 20% of the activity of porcine insulin in in vitro insulin assays using human cells in culture. [Val2-A]insulin displays 20-22% of the activity of bovine insulin in in vitro insulin assays using rat liver plasma membranes or isolated rat adipocytes. We suggest that the substitution of valine for isoleucine at position A2 is responsible for all or most of the diminution in potency of owl monkey insulin relative to porcine insulin. The data are discussed with regard to previous findings with insulin analogues in which isoleucine A2 was replaced with norleucine, glycine and alanine.