Proteinase occurrence

Proteinase K is obtained from Beckman (Somerset, NJ). Other sources may be acceptable In using alternate sources, the occurrence of blue backgrounds between colonies, and oversize, blurry signals at colony sites after the final color development step indicates insufficient proteolytic activity. Prepare a solution of 200 pg/mL in IX SSC... 

The ubiquitous occurrence of proteinases is accompanied by a similar distribution of fairly specific proteins that inhibit these enzymes. In normal health, there is a delicate balance between the levels of enzymes and their macromolecular inhibitors. This balance is particularly important in the blood-clotting clot-lysis scheme. Since the total volume of blood in the adult human body is only about 5 1, a massive response is required in the event of an injury that results in a rapid haemorrhage. Some positive feedback is present in the blood-clotting mechanism in order to achieve this rapid response, but clearly this must be sensitively controlled by endogenous inhibitors if a thrombosis is not to occur. 

Various hydrolases are in fact associated with the protein bodies, though we should realize that some of the enzymes may be contaminants from the cytoplasm. Acid proteinases have been found in protein bodies of Gossypium [47, 79], V faba [54], Hordeum [55] and Cannabis [66]. In the last, the proteinase is active against the crystalloid moiety (edestin) and has, therefore, been called edestinase [66]. The occurrence of these various enzymes for the hydrolysis of the native protein therefore suggests the possible lysosomal nature of protein bodies. 

Hydrolases identified include amylases, lipases, esterases, proteinases and phosphatases. Proteinase inhibitors have also been found. Important oxidoreductases in milk are aldehyde dehydrogenase (xanthine oxidase), lactoperoxidase and catalase. A general idea of the occurrence and localization of enzymes in boving milk is given in Table 10.24... 

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