. The chemical activities of bacteria. Bacteria. 72 THE FORMATION OF ENZYMES IN BACTERIA investigation of the amount of enzyme formed in the cell at various growth ^H values shows a direct relation between the formation of the neutralising mechanism, suppression of the non-neutralising mechanisms, and the ;pH of the environ- ment (see Fig. 2). (6) Protective mechanisms: the function of some enzymes such as catalase is to destroy metabolites which, if allowed to accumulate, would prove toxic to the cell. All enzymes are optimally active at a definite ^H and, conse- quently, as the environment p
. The chemical activities of bacteria. Bacteria. 72 THE FORMATION OF ENZYMES IN BACTERIA investigation of the amount of enzyme formed in the cell at various growth ^H values shows a direct relation between the formation of the neutralising mechanism, suppression of the non-neutralising mechanisms, and the ;pH of the environ- ment (see Fig. 2). (6) Protective mechanisms: the function of some enzymes such as catalase is to destroy metabolites which, if allowed to accumulate, would prove toxic to the cell. All enzymes are optimally active at a definite ^H and, conse- quently, as the environment pH diverges from this pH of o X •^ 40-. -100^ 80° < pH OF MEDIUM DURING GROWTH Fig. 2. Variation of formation of glutamic acid decarboxylase and deaminase of Esch. coli with the pB. of the medium during growth. optimal activity, the effectiveness of each enzyme unit decreases. This means that in the case of catalase, which has optimal activity at ^H 6-5, the enzyme unit is considerably less effective during growth occurring at pH 9 than at pH 6-5. In such cases we sometimes find that the organism compensates for this loss of efficiency per enzyme unit by the production of more enzyme so that the effective activity (= No. of enzyme units X activity of each unit at the environmental pH) is roughly constant whatever the pB. in the medium. Enzymes whose formation is affected by pH in this way are urease, catalase, formic, and alcohol dehydrogenases—enzymes whose. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gale, E. F. (Ernest Frederick). New York, Academic Press
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