Neutral active hyaluronidases

Based on their pH-dependent activity profile, hyaluronidases are classified into two groups. Acid active hyaluronidases are active between pH 3 and 4, and this group includes human liver and serum hyaluronidases. Neutral active hyaluronidases are active between pH 5 to 8 and include PH-20, snake venom, and bee venom hyaluronidases [122],... 

Alternatively, the calcium stores may be concentrated by lamellar bodies from the intercellular fluids released during terminal differentiation. The lamellar bodies are thought to be modified lysosomes containing hydrolytic enzymes, and a potential source of the hyaluronidase activity. The lamellar bodies fuse with the plasma membranes of the terminally differentiating keratinocytes, increasing the plasma membrane surface area. Lamellar bodies are also associated with proton pumps that enhance acidity. The lamellar bodies also acidify, and their polar lipids become partially converted to neutral lipids, thereby participating in skin barrier function. 

The first vertebrate hyaluronidase activity to be identified was derived from a testicular extract [188], active at neutral pH. A similar enzyme, but active at acidic pH, was later documented in human serum [189]. Another thirty years passed before sufficient purification was achieved for sequence analysis [172]. 

Solutions of crude preparations of hyaluronidase can be stored frozen for several months without losing important amounts of activity [26,50,73]. Purified hyaluronidase rapidly loses all activity when stored frozen unless stabilizing agents like detergents or high concentrations of salts are added [63]. At neutral pH, solutions of hyaluronidase can be stored at room temperature for several days [50], The temperature profile of activity of the enzyme shows a sharp decline at a temperature of about 50°C. Hyaluronidase is rapidly inactivated when stored at 55-60°C [14,50,52], but it can be kept at 40°C for at least one hour without losing activity [30,50]. 

The complexes are not glycoproteins, but involve the adsorption of the enzyme on polysaccharide. The evidence for the association comes from the isolation from soil, using buffer extraction, of active enzyme fractions which, on hydrolysis, yield the usual rainge of neutral sugars common to soil. Dissociation of the enzymes (lysozyme and hyaluronidase) from the carbohydrate occurs on treatment with sodium dodecyl sulphate, which would not separate covalently linked components. This evidence does not rule out the possibility that the association occurs during coextraction. 

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