Hyaluronidase

Hyaluronidases are a family of enzymes that catalyse the degradation of hyaluronic acid (HA). Karl Meyer classified these enzymes in 1971 into three distinct groups, a scheme based on the enzyme reaction products. The three main types of hyaluronidases are two classes of eukaryotic endoglycosidase hydrolases and a prokaryotic lyase-type of glycosidase. Hyaluronidases are a family of enzymes that catalyse the degradation of hyaluronic acid (HA). Karl Meyer classified these enzymes in 1971 into three distinct groups, a scheme based on the enzyme reaction products. The three main types of hyaluronidases are two classes of eukaryotic endoglycosidase hydrolases and a prokaryotic lyase-type of glycosidase. In humans, there are five functional hyaluronidases: HYAL1, HYAL2, HYAL3, HYAL4 and HYAL5 (also known as SPAM1 or PH-20); plus a pseudogene, HYAL6 (also known as HYALP1). The genes for HYAL1-3 are clustered in chromosome 3, while HYAL4-6 are clustered in chromosome 7. HYAL1 and HYAL2 are the major hyaluronidases in most tissues. GPI-anchored HYAL2 is responsible for cleaving high-molecular weight HA, which is mostly bound to the CD44 receptor. The resulting HA fragments of variable size are then further hydrolized by HYAL1 after being internalized into endo-lysosomes; this generates HA oligosaccharides. According to their enzymatic mechanism, hyaluronidases are hyaluronoglucosidases (EC 3.2.1.35), i.e. they cleave the (1->4)-linkages between N-acetylglucosamine and glucuronate. The term hyaluronidase may also refer to hyaluronoglucuronidases (EC 3.2.1.36), which cleave (1->3)-linkages. In addition, bacterial hyaluronate lyases (EC 4.2.2.1) may also be referred to as hyaluronidases, although this is uncommon. By catalyzing the hydrolysis of hyaluronan, a constituent of the extracellular matrix (ECM), hyaluronidase lowers the viscosity of hyaluronan, thereby increasing tissue permeability. It is, therefore, used in medicine in conjunction with other drugs to speed their dispersion and delivery. Common applications are ophthalmic surgery, in combination with local anesthetics. It also increases the absorption rate of parenteral fluids given by hypodermoclysis, and is an adjunct in subcutaneous urography for improving resorption of radiopaque agents. Hyaluronidase is also used for extravasation of hyperosmolar solutions. Hyalurodinase is used by plastic surgeons and dermatologists to reverse the effects of hyaluronic acid injections used as dermal fillers whenever the patient receiving the injections is unhappy with the results. Brand names of animal-derived hyaluronidase include Hydase (developed and manufactured by PrimaPharm Inc., distributed by Akorn Inc.), which has been FDA-approved as a 'thimerosal-free' animal-derived hyaluronidase, Vitrase (Bausch + Lomb/Valeant Pharmaceuticals), Amphadase (Amphastar Pharmaceuticals), and Wydase. Wydase, however, is no longer manufactured. On December 2, 2005, the United States FDA approved a synthetic (recombinant or rDNA) 'human' hyaluronidase, Hylenex (Halozyme Therapeutics). The FDA also approved HyQvia (Shire) in late 2014, a form of subcutaneous immunoglobulin (SCIG) that uses Hylenex to allow for a far greater volume of SCIG to be administered than would normally be possible to administer subcutaneously, providing a form of SCIG that can be dosed on a monthly basis, a longer period of time than other forms of SCIG allow. HyQvia had a rate of systemic adverse effects higher than traditional subcutaneous forms of immunoglobulin injection, but lower than those typical in IVIG patients. Also in epidural lysis of adhesions for pain management. Hyaluronidase is a recommended antidote for vinca alkaloid overdose or extravasation. The role of hyaluronidases in cancer has been historically controversial due to contradictory observations, namely that levels of hyaluronidase (HYAL1/2) are increased in some cancers (colorectal, bladder, prostate, breast and brain), whereas low expression of HYAL1 is correlated with a decrease in survival of pancreatic adenocarcinoma patients. The reason for this apparent contradiction is that both the accumulation of HA (due to increased HAS levels and decreased HYAL levels), and the degradation of HA into HA oligosaccharides by high HYAL levels result in increased tumor malignancy. Elevated tissue expression of hyaluronic acid and hyaluronidase validates the HA-HAase urine test for bladder cancer. Limited data support a role of lysosomal hyaluronidases in metastasis, while other data support a role in tumor suppression. Other studies suggest no contribution or effects independent of enzyme activity. Non-specific inhibitors (apigenin, sulfated glycosaminoglycans) or crude enzyme extracts have been used to test most hypotheses, making data difficult to interpret. It has been hypothesized that, by helping degrade the ECM surrounding the tumor, hyaluronidases help cancer cells escape from primary tumor masses. However, studies show that removal of hyaluronan from tumors prevents tumor invasion. Hyaluronidases are also thought to play a role in the process of angiogenesis, although most hyaluronidase preparations are contaminated with large amounts of angiogenic growth factors.