Proteinases of the medicinal leech, Hirudo medicinalis: purification and partial characterization of three enzymes from the digestive tract.

1. Three different proteinases were isolated from intestinal extracts of Hirudo. 2. The action on synthetic substrates and the effect of various inhibitors indicate that one is a trypsin-like enzyme whereas the other two are chymotryptic. 3. This was confirmed by analysing the degradation of the insulin B-chain. 4. The relative molecular masses of all enzymes are approximately 35,000 and the isoelectric points 9.03, 9.12 and 9.41, respectively. 5. The specific activities assayed with SAPPNA are very high in comparison with proteinases of other animals.