Hyaluronidases molecules

Oligosaccharides ranging from two to six repeating units were prepared by testicular hyaluronidase digestion of hyaluronate, and isolated by Sephadex G-50 chromatography. Experiments were carried out to determine the minimum chain length of hyaluronate to which core molecules would bind. When core molecules were mixed... 

Tissues that contain high molecular weight HA are unusually resistant to invasion and penetration.49 Blood vessels are unable to penetrate joint synovium, cartilage, and the vitreous of the eye. It is also unusual for tumor metastases to develop in these structures. It may be the large size of the HA polymer that also protects such structures from invasion by parasites. The mechanism by which such high molecular weight structures resist hyaluronidase degradation, and avoid the rapid HA turnover characteristic of the rest of the body is not known. Potent hyaluronidase inhibitors may be involved, a class of molecules about which little is known. 

A vertebrate homologue of the cell cycle control protein CDC37 was recently cloned and found to be an hyaladherin,62 as was a protein that copurified with the splicing factor SF2.63 An intracellular form of the HA receptor RHAMM was demonstrated to regulate erk kinase activity. Changes in function of these intracellular, depending on whether or not they have HA molecules attached, confers another layer of complexity dependent on intracellular hyaluronidase enzymes. 

If inhibition of HA degradation by hyaluronidase occurs, then a class of molecules that have not been explored, the hyaluronidase inhibitors, are very important. It can be postulated that with extreme stress, hyaluronidase inhibitors would be found in the circulation as acute phase proteins, the stress response products synthesized by the liver. These would prevent the ever-present rapid destruction and allow levels of HA to quickly increase. 

The determination of the diffusion behavior of larger molecules in a given tissue prior to and after the digestion with hyaluronidase is an established method to investigate the limitations of diffusion in a given tissue [62]. 

HA is a major molecule in joint fluid, and plays a major role in that tissue in joint motion and maintenance of normal joint homeostasis. In inflammatory diseases of the joint such as rheumatoid arthritis (RA), and in degenerative joint disease such as osteoarthritis (OA), the levels and average molecular size of HA chains are much reduced. Expressions of both HASl and 2 are decreased, while the hyaluronidases are increased in the various forms of arthritis, compared to control, with a concomitant decrease in average molecular sizes [112]. 

The molecular size of viscoelastics protects from diffusion. Viscoelastics pass out of the eye through the trabecular meshwork as a large, usually unchanged molecule (Berson, Patterson 8c Epstein, 1983). As contractile elements are present both within the trabecular meshwork and ciliary body, this process is probably dynamic (Balazs, 1983). Several rabbit studies prove that sodium hyaluronate is carried away by both the episcleral veins as well as the mucoscleral pathway, followed by hyaluronidase break down within the tissues (Iwata, Miyauchi 8c Ta-kehana, 1984 Iwata 8c Miyauchi, 1985 Miyauchi 8c Iwata, 1984,1986). 

Figure 10.20 Hyaluronidase induces the cleavage of the glycosidic bond of the hyaluronic acid molecule.

Hyaluronidase induces the cleavage of the glycosidic bond of the HA molecule, which is a covalent bond that joins a carbohydrate molecule to another group (Fig. 10.20). 

Type 3. Microbial hyaluronidases (e.g. Streptococcus hyaluronidase). Microbial hyaluronidases hydrolyse p-N-acetylaminoglycoside bonds of a substrate and simultaneously dehydrate the residue of uronic acid at the non-reducing terminus of the molecule. Substrate specificity of bacterial hyaluronate lyases varies considerably in the different species of microbe producers. Hyaluronidase of Streptococcus pneumoniae has the highest substrate specificity it hydrolyses HA alone and does not destroy other glucosami-noglycans [43]. The hyaluronate lyase, when isolated from Streptococcus pneumoniae, reaches optimal activity at pH 6.0 with the Michaelis constant with respect to HA being equal to 3.8x 10" mol/l (in terms of Michaelis-Menten kinetics) [44]. The presence of Cd3 (about 10 mM) is necessary in order to show the maximum enzyme activity. 

Some extracellular enzymes produced by microorgcinisms are known to be protected by association with co-secreted polysaccharide molecules. This could form a basis for the observation that a range of enzymes, including invertase, cellulase, phosphatase, proteases, B-glucosidase, lysozyme and hyaluronidase exist in soil in complexes with carbohydrate which serves to protect them against denaturation or proteolysis ... 

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