we conclude that ( a ) processing of proinsulin to insulin in vivo as in vitro likely occurs by preferential cleavage at the arg32-glu33 peptide bond in proinsulin , ( b ) proinsulin is inefficiently processed in the vascular compartment , and ( c ) subcutaneous administration of the precursor can result in the formation of conversion intermediates with the potential for contributing to biological activity .
C0021641
insulin
C0033362
proinsulin