Membrane-bound cell surface peptidases in reproductive organs

Membrane-bound cell surface peptidases including aminopeptidase-N (EC 3.4.11.2), dipeptidyl peptidases IV (EC.3.4.14.5), carboxypeptidase-M (EC 3.4.17.12), neutral endopeptidase (EC 3.4.24.11) and endothelin converting enzyme-1 (EC 3.4.23) were shown to be differently expressed on human ovarian granulosa, theca interna and luteal cells and on endometrial epithelial and stromal cells. These peptidases have their catalytic sites extracellularly and can metabolize biologically active peptides at the cell surface, serving as local regulators of peptide concentrations. In the ovary and endometrium, numerous peptides are considered to be locally produced and play an important role in the follicular growth, ovulation, corpus luteum function, endometrial differentiation and embryo implantation in an autocrine and/or paracrine fashion. The inhibition of aminopeptidase activity by bestatin affected murine follicular growth, steroidogenesis by porcine ovarian cells and progesterone-induced decidualization of human endometrial stromal cells in vivo or in vitro. These findings suggest that membrane-bound peptidases are important regulators of the function and differentiation of the ovarian cells and endometrial cells including embryo. In the near future, the physiological roles of these peptidases will be clarified and clinical use of peptidase inhibitors may be applied to the various reproductive disorders.