BEE VENOM HYALURONIDASE IS HOMOLOGOUS TO A MEMBRANE-PROTEIN OF MAMMALIAN SPERM

The venom of honeybees, Apis mellifera, contains several biologically active peptides and two enzymes, one of which is a hyaluronidase. By using degenerate oligonucleotides derived from the amino-terminal sequence of this hyaluronidase reported by others, clones encoding the precursor for this enzyme could be isolated from a cDNA library prepared from venom glands of worker bees. The deduced amino acid sequence showed that bee venom hyaluronidase is a polypeptide composed of 349 amino acids containing four cysteines and three potential sites for N-glycosylation. The sequence of the precursor also indicated that the conversion of the pro-enzyme to the end product must involve cleavage of a Thr-Pro bond, a most unusual processing reaction. The mRNA encoding hyaluronidase could also be detected in testes from drones. Expression of the cloned cDNA in Escherichia coli yielded a 41-kDa polypeptide that had hyaluronidase activity. Interestingly, the hyaluronidase from bee venom glands exhibited significant homology to PH-20, a membrane protein of guinea pig sperm involved in sperm-egg adhesion. These structural data support the long-held view that hyaluronidases play a role in fertilization.