Biology of Reproduction, Vol 24, 879-887, Copyright © 1981 by Society for the Study of Reproduction

Properties of a Membrane-Associated L-Leucine -Naphthylamidase (Leucine Aminopeptidase) from the Porcine Uterus

¹ Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610
² Department of Animal Science, University of Florida, Gainesville, Florida 32610

An amino acid arylamidase (leucine -napthylamidase), which appears to be localized predominantly in the surface epithelium of the pig uterus, did not show any marked changes in specific activity during the estrous cycle or pregnancy. The arylamidase was solubilized by extraction of crude microsomes derived from endometrium by 2% (v/v) Triton X-100 or by proteolytic treatment. In the latter case, a water soluble polypeptide of MW 480,000 was released which was purified over 2000-fold relative to the original homogenate by successive chromatography on columns of DEAE-cellulose, Sepharose CL-6B and L-leucylglycine immobilized on agarose. The enzyme so isolated had an apparent Km of 0.14 mM and a pH optimum around 7. Its activity was stimulated by Co²⁺, but inhibited by chelating agents. It resembled epithelial brush border aminopeptidases of the M class (EC 3.4.11.2), as well as a progesterone-induced, secreted form of -naphthylamidase described earlier. It is suggested that such soluble forms of uterine naphthylamidases are probably derived secondarily from the surface membrane of the uterus by in vivo proteolytic activity.