Max-Planck-Institut für Immunbiologie, D-78 Freiburg, West Germany
(Received 18th February 1975)
The activity of a leucine-β-naphthylamide-splitting enzyme has been shown histochemically to increase markedly before implantation and to reach a sharp peak at 5-6 days post coitum (p.c.) (Denker, 1969; see also description of unmated and 6 days p.c. stages by Petry et al., 1970). The enzyme has been referred to as 'leucine aminopeptidase'. Recently, however, it has become customary to call this class of enzymes 'amino acid arylamidases' or 'amino acid naphthylamidases', because they exhibit properties which differ from those of classical leucine aminopeptidase (cytosol aminopeptidase, EC 126.96.36.199). Amino acid arylamidases are more related to EC 188.8.131.52, but definitive classification is still lacking (see Patterson et al., 1963; for discussion and recent references see Bergmeyer, 1974; Pearse, 1972; Denker & Stangl, 1974).
In the present study the activity of the enzyme at and between the implantation sites was compared.