The use of dipeptide-p-nitranilides for the study of 2 placental aminopeptidases separated on Sephadex G200 helped in establishing some regular features of their specifities. The high-molecular (320,000 daltons) one prefers Phe in position P'1 to Leu, whereas the lower-molecular aminopeptidase (145,000 daltons) prefers Leu. The high-molecular aminopeptidase splits very slowly the N-terminal Leu when Gly is in adjacent position. Leu-Gly-p-NA is therefore an inhibitor of this AP.

From 4 serum aminopeptidases (2 of pregnant and 2 of nonpregnant women's sera), the placental lysosomal (mol. wt 320,000) splits Lys-NAp only. B-Cys-NAp is hydrolyzed from the both placental enzymes, i.e. lysosomal and microsomal (mol. wt 145,000) AP. Ala-NAp is split by both nonpregnant serum AP more readily than Leu-NAp.

In the myometrium and endometrium a content of plasminogen activator and non-specific trypsin-like proteases was determined. It was ascertained that there was a higher level of plasminogen activator in the endometrium during the menstruation in the contrary to the first and second phase of the menstrual cycle and that both plasminogen activator and non-specific trypsin-like proteases were relative higher in Corpusmyometrium than those Cervixmyometrium. The proteases present in the fractions of myometriumeluate were able to split casein and partially fibrin, too. These activities were not inhibited by epsilon aminocaproic acid and aprotinin. The importance of these findings for gynaecological bleeding was suggested.