The activity of enzymic and acidic digests of insulin

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Abstract
Crystalline chymotrypsin, trypsin and pepsin degrade crystalline insulin to give peptide fractions which show no hypoglycemic activity. Digestion by purified crystalline trypsin causes considerable loss of activity although little nonprotein N is formed. The remaining activity shown by the whole digests is precipitable at pH 5.5, and is probably due to intact insulin still present. Variation of the pH of digestion affects the rate but fails to give active fractions. Hydrolysis with 8N and 0.8 N HC1 at low temps. similarly destroys the activity, and the non-protein fractions formed during hydrolysis have no activity. Ether, trichloroacetic acid, 5 [image] urea and diisopropylfluorophosphonate have no appreciable effect on the activity of insulin in periods of contact up to 24 hrs.
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