Comparative reduction/oxidation studies with single chain des-(B30) insulin and porcine proinsulin

The single chain des-(B30) insulin molecule (SCI) has been reduced and reoxidized together with porcine proinsulin (PPI). Yields of correctly folded and reoxidized SCI and PPI were analyzed by HPLC. The concentrations of both proteins were 10(-3) M during reduction and 10(-5) M during oxidation. The pH during reoxidation was varied from 8.6 to 9.2 and the temperature from 4 to 37 degrees. Under all conditions tested, the recovery of SCI was substantially higher than that of PPI. The recoveries peaked after 24-72 h. It is suggested that the "miniproinsulin" SCI folds correctly up more efficiently than porcine proinsulin, resulting in higher yields of reoxidized SCI.