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Most enzymes are sensitive to pH and have specific ranges of activity. All have an optimum pH. The pH can stop enzyme activity by denaturating (altering) the three-dimensional shape of the enzyme by breaking ionic, and hydrogen bonds. Most enzymes function between a pH of 6 and 8; however pepsin in the stomach works best at a pH of 2 and ...
The effects of temperature on enzyme activity. Top: increasing temperature increases the rate of reaction (Q10 coefficient). Middle: the fraction of folded and functional enzyme decreases above its denaturation temperature. Bottom: consequently, an enzyme's optimal rate of reaction is at an intermediate temperature.
The latter condition is of particular practical interest, since commercial restriction enzymes are usually supplied in a buffer containing a substantial amount of glycerol (50% v/v is typical), meaning insufficient dilution of the enzyme solution can cause star activity; this problem most often arises during double or multiple digests.
Pepsin may be inhibited by high pH (see Activity and stability) or by inhibitor compounds. Pepstatin is a low molecular weight compound and potently inhibitor specific for acid proteases with an inhibitory dissociation constant (Ki) of about 10 −10 M for pepsin.
Physiologically normal intracellular pH is most commonly between 7.0 and 7.4, though there is variability between tissues (e.g., mammalian skeletal muscle tends to have a pH i of 6.8–7.1). [4] [5] There is also pH variation across different organelles, which can span from around 4.5 to 8.0. [6] [7] pH i can be measured in a number of ...
A decade before Michaelis and Menten, Victor Henri found that enzyme reactions could be explained by assuming a binding interaction between the enzyme and the substrate. [11] His work was taken up by Michaelis and Menten, who investigated the kinetics of invertase, an enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose. [12]
The L. lactis strain is stable over the pH range of 6.5 to 11.0, and the L. brevis enzyme, which is less tolerant of pH changes, show activity over the pH range of 5.7–7.0. [14] Thermal tests were also done by Kei Y. and Noritaka T. and the xylose isomerase was found to be thermally stable to about 60 degrees Celsius [ 14 ]
Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. [5] It is a very important enzyme in protecting the cell from oxidative damage by reactive oxygen species (ROS).