Characterization and immunolocalization of beta-D-glucuronidase in mouse testicular germ cells and spermatozoa

Spermatozoa released from the seminiferous tubules are terminally different iated cells with no known synthetic activity. Their components are synthesi zed in the spermatogenic cells during spermatogenesis. In this study, we re port the characterization and immunolocalization of beta-glucuronidase in m ouse testicular germ cells and spermatozoa. The enzyme is an exoglycohydrol ase with dual localization, being present in lysosomes and endoplasmic reti culum of several mouse and rat tissues. The purified germ cell preparations (spermatocytes, round spermatids, and condensed/elongated spermatids) when assayed for beta-glucuronidase activity showed that the spermatocytes cont ained five times more enzyme activity per cell than the spermatids, Polyacr ylamide gel electrophoresis, carried out under native and denaturing condit ions, demonstrated that the germ cells express only the lysosomal form of t he enzyme (pl 5.5-6.0) with a subunit molecular mass of 74 kDa, Immunocytoc hemical studies revealed a positive reaction in the Gels membranes, Golgi-a ssociated vesicles, and lysosomes of late spermatocytes (pachytene spermato cytes) and a stage-specific localization during spermiogenesis. The forming or formed acrosome of the elongated spermatids (stages 9-16) and epididyma l spermatozoa was highly immunopositive. Comparison of immunoprecipitation curves and kinetic properties of the enzyme present in spermatocytes and sp ermatozoa revealed no major differences. Taken together, our results demons trate that beta-glucuronidase activities present in the lysosomes of sperma tocytes and the sperm acrosome are kinetically and immunologically similar. (C) 1999 Academic Press.