Factors Affecting Enzyme Activity

Yamane, T., Ichiryu, T., Nagata, M., Ueno, A., and Shimizu, S., Intramolecular esterification by lipase powder in microequeous benzene factors affecting activity of pure enzyme, Biotechnol. Bioeng., 36, 1063-1069, 1990. 

The activity displayed by enzymes is affected by a variety of factors, some of which are essential to the harmony of metabolism. 

Lipases have also been used as initiators for the polymerization of lactones such as /3-bu tyro lac tone, <5-valerolactone, e-caprolactone, and macrolides.341,352-357 In this case, the key step is the reaction of lactone with die serine residue at the catalytically active site to form an acyl-enzyme hydroxy-terminated activated intermediate. This intermediate then reacts with the terminal hydroxyl group of a n-mer chain to produce an (n + i)-mer.325,355,358,359 Enzymatic lactone polymerization follows a conventional Michaelis-Menten enzymatic kinetics353 and presents a controlled character, without termination and chain transfer,355 although more or less controlled factors, such as water content of the enzyme, may affect polymerization rate and the nature of endgroups.360... 

Table 47-11. Some factors affecting the activities of glycoprotein processing enzymes.

Various factors affect the activities of the enzymes metabolizing xenobiotics. The activities of these enzymes may differ substantially among species. Thus, for example, the possible toxicity or carcinogenicity of xenobiotics cannot be extrapolated freely from one species to another. There are significant differences in enzyme activities among individuals, many of which appear to be due to genetic factors. The activities of some of these enzymes vary according to age and sex. 

Most enzymes are very specific in their activity, and each chemical reaction in a living organism requires a specific enzyme. Their specificity arises from what is known as an active site, a location in the enzyme s molecule that has a shape matching that of a part of the molecule with which it reacts. The activity of the enzymes is affected by such factors as temperature and pH, each enzyme functioning best within a specific range of temperatures and pH. Outside this range the enzymes are structurally altered and their activity is either impaired or terminated. 

Not every fishing system works as well and preserves fish as long as the ones used in Iceland and Norway. Spoilage at sea is very common and contributes substantially to the loss of fishery resources. Several factors affect the keeping quality of fish held cai trawlers. One factor is the temperature of the water from which the catch is taken. Fish from hi temperature water needs less chilling to inhibit enzyme activity fish from very low temperature waters need very low temperature chilling to retard enzyme activity (13). 

It is the principal factor affecting the water activity of young cheeses and has a major effect on the growth and survival of bacteria and the activity of enzymes in cheese, and hence affects and controls the biochemistry of cheese ripening. 

Most, if not all, milks contain sufficient amounts of lipase to cause rancidity. However, in practice, lipolysis does not occur in milk because the substrate (triglycerides) and enzymes are well partitioned and a multiplicity of factors affect enzyme activity. Unlike most enzymatic reactions, lipolysis takes place at an oil-water interface. This rather unique situation gives rise to variables not ordinarily encountered in enzyme reactions. Factors such as the amount of surface area available, the permeability of the emulsion, the type of glyceride employed, the physical state of the substrate (complete solid, complete liquid, or liquid-solid), and the degree of agitation of the reaction medium must be taken into account for the results to be meaningful. Other variables common to all enzymatic reactions—such as pH, temperature, the presence of inhibitors and activators, the concentration of the enzyme and substrate, light, and the duration of the incubation period—will affect the activity and the subsequent interpretation of the results. 

The levels of cardiovascular factors could also be influenced by the ability of vitamin E to affect activation of arachidonic acid from membrane phospholipids by phospholipase A2. Vitamin E, either given in the diet or by incubation with platelets themselves, was found to inhibit phospholipase A2 in a dose-dependent manner. a-Tocopheryl acetate had little or no effect on the activity of this enzyme, but tocol, without methyl groups in the chroman ring, was more potent than either (+)- or ( )-a-tocopherol, suggesting that the methyl groups were not important for the inhibition but the hydroxy group in the ring was critical for activity [131]. 

The action spectrum for DDT and its structural analogs is known to be quite broad and cannot be attributed to simple enzyme inhibition, as in the case of the carbamates or the organophosphates. The presence of chloroaryl moieties, as well as steric effects at receptor sites, both appear to be factors affecting insecticidal activity. In addition to DDT itself, its metabolites DDE and DDA and DDD have some activity. Efforts to overcome insect resistance and to produce more biodegradable analogs led to the introduction of substituents other than chlorine for... 

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