Hyaluronidase 4/HYAL4 Proteins and Enzymes

Hyaluronidases (HYALs) are a group of five endo beta N-acetyl hexosaminidases that include HYAL1, HYAL2, HYAL3, HYAL4, and SPAM1/PH20. HYAL1, HYAL2 and SPAM1 are endo beta N-acetyl glucosaminidases that are primarily active on hyaluronan, while HYAL4 is primarily active on chondroitin sulfate (type C and D in particular). The backbone of chondroitin sulfate is composed of repeating units of -4GlcA beta 1-3 GalNAc beta 1-, and it most closely resembles that of hyaluronan (repeating units of -4GlcA beta 1-3 GlcNAc beta 1-). HYAL4 is believed to specifically degrade chondroitin sulfate in the lysosome, as its optimal pH for activity is approximately 4.5.