Hydrolyzes high molecular weight hyaluronic acid to produce an intermediate-sized product which is further hydrolyzed by sperm hyaluronidase to give small oligosaccharides. Displays very low levels of activity. Associates with and negatively regulates MST1R (By similarity). Random hydrolysis of (1->4)-linkages between N-acetyl-beta-D-glucosamine and D-glucuronate residues in hyaluronate. Interacts with MST1R. Widely expressed. In the brain, expressed during embryonic stages but expression decreases after birth and is barely detectable in adult brain. Belongs to the glycosyl hydrolase 56 family. Was originally thought to be lysosomal.