Two kinds of hyaluronidases (HD) differing in molecular weight were highly purified from the bovine testicle and their physicochemical and enzymatic properties were studied. By isoelectric focusing both HDs of high (H-HD ; MW 93300) and low (L-HD ; MW 69200) molecular weight were found to be composed of three kinds of subforms with different isoelectric points. It was also recognized that both H-HD and L-HD are glycoproteins consisting of a single polypeptide chain and that the treatment of H-HD with proteinase lowered its molecular weight to achieve its conversion into L-HD. The results obtained by enzyme kinetic study clarified that the affinity of H-HD for the substrate was twice that of L-HD. Therefore, it was considered that the native HD in the bovine testicle is H-HD, which affinity for the substrate was reduced as a result of a lowering of its molecular weight for its conversion into L-HD by the action of hroteinase contained in the bovine testicle extract.
