Rigor enzyme changes

Standard tests, dialysis, heat inactivation, and the effects of changing the pH on the catalytic activity of the preparations, were all consistent with the idea that enzymes had the properties ascribed to proteins. Between 1920 and 1930 increasing numbers of enzymes were isolated by Willstatter and partially purified. Assays for purification and the extent achieved were not sufficiently rigorous to exclude the possi-... 

Following the in vitro discovery that a particular metabolic pathway is mediated by a single CYP isoform and that such metabolism is a major route of elimination, it is not uncommon to speculate that appropriate assessment of the formation of the metabolite in vivo could serve as a phenotypic trait measure (see Chaps. 3 and 7). Moreover, knowledge of the disposition of the drug and metabolite may indicate a putative quantitative trait for this purpose, e.g., urinary MR. However, considerably greater effort and information is, in fact, required before such a trait value can be accepted as a valid measure of the enzyme s metabolic activity. Unfortunately, several of the earlier-developed in vivo probes were not rigorously evaluated prior to their application, and interpretation of differences/changes in their trait values is therefore not easy. 

It is evident that the complex network of metabolic reactions must be rigorously regulated. At the same time, metabolic control must be flexible, to adjust metabolic activity to the constantly changing external environments of cells. Metabolism is regulated through control of (1) the amounts oj enzymes, (2) their catalytic activities, and (3) the accessibility of substrates. 

Before the influence of freezing was studied, it was necessary to determine whether postmortem (p.m.) storage of muscle at temperatures above freezing (+4°C) influenced the subcellular distribution of the enzymes investigated. As is well known, storage of muscle p.m. results in drastic changes such as development of rigor mortis and a decline in pH from above 7 to about 5.5. 

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