Properties and Functions of Hyaluronidases

Mammal hyaluronidases such as testicular hyaluronidase hydrolyse p-1,4-glycoside bonds inside the HA chain, forming oligosaccharides of different sizes. After prolonged incubation, the final products are mainly hexa- and tetrasaccharides [37]. Mammal hyaluronidases do not have absolute substrate specificity and could hydrolyse chondroitin-4-sulfate, chondroitin-6-sulfate and dermatansulfate. In addition, these enzymes have transglycosilate activity (more details about hyaluronidase isoforms and properties in the human somatic tissues and body fluids are described in [45]). 

In microbiologic technologies of HA production it is fragmented by the bacterial hyaluronidases that are transported into the cultural media. They are called hyaluronate lyases because they are endo-p-acetylhexosamine eliminases. The most typical representative of this class of enzymes are the Streptococcus hyaluronate lyases. The bacterial hyaluronate lyases hydrolyse endo-p-1,4-glycoside bonds in HA via the p-elimination reaction, the result of it is the formation of 4,5-unsaturated oligosaccharides of different lengths. 

The final product of the enzymatic cleavage is a 4,5-unsaturated disaccharide. Therefore, depolymerization of HA with bacterial hyaluronate lyases can be controlled not only by viscometric but also spectrophotometric methods as well. Unlike bacterial hyaluronidase, those from animal tissues are able to fragmentize HA, which could result in the production of saturated oligosaccharides. 

The most appropriate enzyme for the fragmentation of pure HA is testicular hyaluronidase. It hydrolyses HA through the formation of the saturated oligosaccharides (which are important for therapeutic use), is active in the wide pH range 4.0-7.0 and has high thermal stability (it can maintain enzymatic activity up to 50°C). 

Bacterial hyaluronate lyases have a narrow substrate specificity. They split HA that has a higher rate in order to lower the molecular weight of the final products. At the same time, they create unsaturated oligosaccharides that are likely to have different therapeutic properties to saturated oligosaccharides. Several unsaturated oligosaccharides were isolated after a treatment with hyaluronate lyases in order to study their properties [46]. The bacterial hyaluronate lyases could help to study kinetics of HA depolymerization using spectropho-tometric methods that allow for the reaction products level of unsaturation to be identified. 

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