Microbial Metabolism

Microbial Metabolism - - Enzyme activity is also influenced...

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Microbial Metabolism - Activities and regulation of enzymes The activity of an enzyme (the rate of the reaction catalyzed by the enzyme) is influenced by a variety of factors - Every enzyme has an optimum temperature at which its activity is highest (Tortora et al., Figure 5.4a) = As with noncatalyzed reactions, reaction rate tends to increase with increasing temperature = At some point, reaction rate drops drastically with increasing temperature, as the enzyme becomes denatured (Tortora et al., Figure 5.5) - The pH of the environment in which an enzyme operates also influences activity Tortora et al., Figure 5.4b), mostly through ionization of carboxy and amino groups - Enzyme activity varies with substrate concentration in a characteristic manner (Tortora et al., Figure 5.4c) = At some level of substrate, the enzyme is said to be saturated, as all active sites are "occupied" = Under normal cellular conditions, reaction rate is more likely to be determined by substrate concentration than by enzyme concentration
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Unformatted text preview: - Enzyme activity is also influenced by (and, in living systems, is often regulated by) inhibitors (Tortora et al., Figure 5.6) = Competitive inhibitors are molecules that compete with the normal substrate for the enzyme's active site (Tortora et al., Figure 5.6b) = Noncompetitive inhibitors bind to a part of the enzyme other than the active site (Tortora et al., Figure 5.6c) The binding site of a noncompetitive inhibitor is called an allosteric site In some cases, allosteric binding of a compound can actually activate enzyme activity = Feedback inhibition (Tortora et al., Figure 5.7) is an important biochemical control mechanism involving allosteric noncompetitive inhibitors In feedback inhibition, the end-product of a reaction sequence acts as an allosteric inhibitor of an enzyme catalyzing a reaction early in the reaction sequence Feedback inhibition is especially important in regulating levels of metabolic intermediatesa...
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