beta-Hexosaminidase of X. laevis: isoforms and characterization in oocytes

MORALES ES, CABADA MO Y ARRANZ SE.

San Miguel de Tucumán

Congreso; XLV Reuinón anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Glycosidases have been proposed to be involved in different fertilization steps as binding, penetration and polyspermy prevention. However, the glycosidase involved in each step remain unclear. Our objective was to characterize X. laevis oocytes glycosidases with a potential role in fertilization. Different glycosidase were analyzed. The main activity found was the N-acetyl-beta-D-glucosaminidase (Hex), which has been reported to participate both in gamete binding and polyspermy prevention. Our in-silico studies showed the existence, so far unknown in amphibians, of two different Hex polypeptides, one corresponding to an alpha and the other to a beta chain. In mammals, they constitute three Hex isoforms: Hex A(alpha-beta), Hex B(beta-beta) and Hex S(alpha-alpha) and are codified by two different genes that evolved from a common ancestor. However, in Xenopus would be produced by alternative splicing from a single gene. In native gels, oocytes Hex corresponded to an A or S isoform. Western blot experiments indicated that, as humans, their polypeptides appear to be synthesized as prepropolypeptides, further proteolyzed to give the mature chains. Histochemical assays shown that Hex is differentially localized in the animal pole of oocytes; the Amphibians sperm entry site. Our evidence suggests the existence of a strategic location of Hex that might directly impact fertilization strategies and polyspermy prevention.