Hypodermin A, a trypsin-like neutral proteinase from the insect Hypoderma lineatum.

Hypodermin A, a serine proteinase from the larva Hypoderma lineatum, with a molecular weight of 27 000 was obtained in pure form by ion-exchange chromatography. It is inhibited by diisopropyl phosphofluorate, a serine proteinase inhibitor, but not by metallo or cysteine enzyme inhibitors such as EDTA or thiol reagents. In the same way, it is fully inactivated by trypsin inhibitors, but not by specific chymotrypsin inhibitors. Its specificity, limited to carboxyl side of arginine residue in B-chain of insulin, is more complicated on other polypeptide substrates. Sequence analysis suggests structural homology with H. lineatum collagenase as well as with other members of the trypsin family.