The hyaluronidase gene HYAL1 maps to chromosome 3p21.2-p21.3 in human and 9F1-F2 in mouse, a conserved candidate tumor suppressor locus.

We recently cloned and expressed the major hyaluronidase activity from human plasma, HYAL1, and found that the protein is 40% identical to the testicular hyaluronidase, PH-20. The HYAL1 mRNA sequence was used in a homology search of the mouse database of expressed sequence tags (dbEST). Two ESTs were obtained and, in combination with 5'RACE-PCR, were used to clone the mouse HYAL1 ortholog (Hyal1). Hyal1 codes for a protein of 462 amino acids that is 73% identical to the human sequence. Hyal1 stably expressed in human embryonic kidney cells resulted in a 20,000-fold increase of hyaluronidase activity. Sequence-tagged sites derived from the HYAL1 gene from both species were used to isolate P1 genomic clones that were used as probes for fluorescence in situ hybridization. The human gene was localized to chromosome 3p21 and the mouse gene to a syntenic region on chromosome 9F1-F2. In mouse, serum hyaluronidase polymorphism has previously been mapped by an interspecific backcross to 60 cM from the centromere of chromosome 9, which corresponds to a cytogenetic location of 9F1-F2. The mouse Hyal1 gene is therefore very likely to be responsible for the hyaluronidase polymorphism linked to this locus. We also present evidence that human HYAL1 is identical to an uncharacterized gene positionally cloned by others from chromosome 3p21.3 that is homozygously deleted in several small-cell lung carcinoma cell lines.

Purification and microsequencing of hyaluronidase isozymes from human urine.

We recently cloned the major hyaluronidase of human plasma, which we termed HYAL1. All hyaluronidase activity could be purified from human urine on an anti-HYAL1 monoclonal antibody column. However, urine contains two hyaluronidases of 57 kDa and 45 kDa, whereas plasma only contains the 57 kDa activity. Microsequencing confirmed that both urinary isozymes have N-termini identical to plasma hyaluronidase, but a second N-terminus was found in the smaller isozyme, apparently derived from the terminal 25 amino acids of HYAL1, at the C-terminus. The two polypeptides of the 45 kDa isozyme resulting from endoproteolytic cleavage of the 57 kDa isoform are presumably linked by disulfide bonds. Sperm contains two isozymes of the testicular hyaluronidase, PH-20, and the lower molecular weight isozyme is believed to be an endoproteolytically processed form of the larger protein. Analogously to PH-20, the smaller isozyme of HYAL1 is likely to be a proteolytically processed product of the larger isozyme.

Purification, cloning, and expression of human plasma hyaluronidase.

Hyaluronidase was purified from human plasma using Triton X-114 phase extractions and ion-exchange chromatography. Monoclonal antibodies generated against the purified protein by a novel screening assay were utilized to isolate homogeneous enzyme for microsequencing. The amino acid sequences obtained matched a cDNA in the Expressed Sequence Tag database which, with 5'-RACE-PCR, was used to clone the plasma hyaluronidase gene, termed Hyal-1. Hyal-1 codes for a protein of 435 amino acids that is over 40% identical to PH-20, a sperm-specific hyaluronidase. Unlike PH-20, which is only expressed in testis, transcripts of Hyal-1 were found in multiple tissues. Hyal-1 stably expressed in human embryonic kidney cells resulted in a 3,000 fold increase of secreted immunoreactive hyaluronidase activity that was biochemically indistinguishable from human plasma hyaluronidase. By immunological, molecular and biochemical criteria, we conclude that Hyal-1 is the predominant hyaluronidase found in human plasma.

Hyaluronidases in tissue invasion.

Hyaluronidases are broadly distributed enzymes with varying substrate specificities, a wide range of pH optima, and different catalytic mechanisms. They may be used by organisms to invade one another. Hyaluronidases have also been invoked as mechanisms for tumor invasion and metastatic spread. In this review, we will concentrate more on the different kinds of hyaluronidases involved in tissue invasion other than cancer metastasis, present some of the rapidly accumulating new data, and address the paradox that both hyaluronidase as well as its hyaluronan substrate are associated with invasion.