Componenti della superficie di uovo e spermatozoo potenzialmente coinvolti nelle interazioni tra gameti in Drosophila melanogaster

We investigated the presence of enzymes on the surface of Drosophila melanogaster spermatozoa that might bind to the carbohydrate residues of the egg shell. Spectrophotometric and fluorimetric studies were used on whole spermatozoa to assay galactosyltransferase and glycosidase activities. No galactosyltransferase is present on the sperm surface, whereas two glycosidases, b-N-acetylglucosaminidase (GlcNAc8ase) and a-mannosidase (Man8ase), have been evidenced. They have an optimal pH of 6–6.5 and 4, respectively. The same glycosidases were detected as soluble forms probably secreted by the seminal vesicle epithelium. We suggest that these enzymes might be involved in the recognition of a-mannose and b-N-acetylglucosamine residues present on the egg shell at the site of sperm entry.