Table 1.
HA-Degrading Proteins | Subcellular Localization/Tissue Distribution | Substrate | End Products of HA Degradation | pH Optimum |
---|---|---|---|---|
HYAL1 | lysosomes/ubiquitous | HA of any size | tetrasaccharides (0.8 kDa) | 3.5 |
HYAL2 | cytoplasmic membranes, ECM/ubiquitous | HMW HA | oligomers (20 kDa) | 4 |
HYAL3 | intracellular/testicles, bone marrow, less other tissues | HA | no hyaluronidase activity | acidic |
HYAL4 | cytoplasmic membranes/placenta, skeletal muscle | chondroitin sulfate | - | - |
PH20 | cytoplasmic membranes/testicles | HA, chondroitin sulfate | tetrasaccharides | neutral, acidic |
TMEM2 (CEMIP2) | cytoplasmic membranes/ubiquitous, placenta | HMW HA | 5 kDa | 6–7 |
CEMIP | cytoplasmic membranes, cytoplasm/lymph node, endometrium | HMW HA * | 10–100 kDa | acidic |
* It remains unclear whether CEMIP has direct catalytic activity as an enzyme. Abbreviations: hyaluronidase (HYAL), hyaluronidase PH-20 (PH20), Transmembrane Protein a type II (TMEM2), Cell Migration Inducing Hyaluronan Binding Protein (CEMIP), extracellular matrix (ECM), hyaluronan (HA), high molecular weight hyaluronan (HMW HA).