Aminopeptidase-B in the rat testes: isolation, functional properties and cellular localization in the seminiferous tubules

• Published in: Molecular and cellular endocrinology 1995-04, Vol.110 (1), p.149-160
• Main Authors: Cadel, Sandrine, Pierotti, Adrian R., Foulon, Thierry, Cre´minon, Christophe, Barre´, Nicole, Segre´tain, Dominique, Cohen, Paul
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Aminopeptidase-B; Aminopeptidases - antagonists & inhibitors; Aminopeptidases - isolation & purification; Aminopeptidases - metabolism; Animals; Blotting, Western; Cations; Exopeptidase; Fluorescent Antibody Technique; Hydrogen-Ion Concentration; Immunoenzyme Techniques; Kinetics; Male; Molecular Sequence Data; Phenanthrolines - pharmacology; Processing; Rats; Rats, Wistar; Residual bodies; Seminiferous Tubules - enzymology; Spermatogenesis; Spermatozoa - enzymology; Substrate Specificity; Testis; Testis - enzymology; Zinc - pharmacology
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/0303-7207(95)03529-G

An aminopeptidase of the B-type, with an apparent M r 72 000 and pI = 4.9, was isolated from rat testes and characterized. The enzyme was able to remove only Arg and/or Lys residues from l-amino acid β-naphthylamide derivatives and from the N-terminus of several peptides. No cleavage occurred in the case of Arg-Pro bonds as found in bradykinin and substance P. The enzyme was sensitive to cysteinyl reagents and to aminopeptidase inhibitors, such as bestatin, amastatin and arphamenines A and B. The aminopeptidase activity, tested with l-Arg β-naphthylamide and with Arg 0-Met-enkephalin as substrates, was inhibited by o-phenanthroline, and restored by Zn 2+ suggesting its metallopeptidase character. The partial characterization of an aminopeptidase-B activity in rat brain cortex identified a protein which is biochemically and immunologically related to the testis enzyme. By immunohistochemistry, the aminopeptidase-B was found to be particularly abundant in the seminiferous tubules at late stages of spermatogenesis and was clearly detected in a restricted area of elongated spermatids. Remarkably, the enzyme was observed to concentrate massively in the residual bodies. Since this aminopeptidase-B was able in vitro to trim out N-terminal Arg and/or Lys residues from peptides mimicking processing intermediates, it is proposed that this enzyme may be involved in propeptide and proprotein processing mechanisms in the course of spermatid differentiation.