Enzyme genetic control

An explanation for the formation of 2jR,3jR-(2,3-c/5)-proanthocyanidins from the 2i ,3S-(2,3-/ra/Z5 )-flavan-3,4-diols could lie in a tautomeric rearrangement of quinone methide intermediates to flav-3-en-3-ols, which could then be stereospecifically converted back to either 2,3-trans or 2,3-cis quinone methides (145). Chemical evidence supporting this thesis has been obtained by the formation of diarylprqpanone derivatives from the reaction of polymeric procyanidins with phenylmethanethiol under alkaline conditions (223). Enzymes controlling the quinone methide to flav-3-en-3-ol rearrangements rather than C-3 inversion of dihydroflavonols may be involved. In either case, evidence continues to mount that the flavan-3,4-diols are indeed central intermediates in the biogenesis of proanthocyanidins and that this conversion is under enzymic (genetic) control (219, 341, 342). 

Biochemistry resulted from the early elucidation of the pathway of enzymatic conversion of glucose to ethanol by yeasts and its relation to carbohydrate metaboHsm in animals. The word enzyme means "in yeast," and the earfler word ferment has an obvious connection. Partly because of the importance of wine and related products and partly because yeasts are relatively easily studied, yeasts and fermentation were important in early scientific development and stiU figure widely in studies of biochemical mechanisms, genetic control, cell characteristics, etc. Fermentation yeast was the first eukaryote to have its genome elucidated. 

Glycogenosis type VI (liver myophosphorylase deficiency) gives rise to hepatomegaly and hypoglycemia in childhood. The enzyme involved is under separate genetic control from the muscle isoform and has been assigned to chromosome 14. 

Red blood cell enzyme activities are measured mainly to diagnose hereditary nonspherocytic hemolytic anemia associated with enzyme anomalies. At least 15 enzyme anomalies associated with hereditary hemolytic anemia have been reported. Some nonhematologic diseases can also be diagnosed by the measurement of red blood cell enzyme activities in the case in which enzymes of red blood cells and the other organs are under the same genetic control. 

The importance of adenosine deaminase in the duration and intensity of sleep in humans has been noted recently (Retey et al. 2005). Animal studies suggest that sleep needs are genetically controlled, and this also seems to apply in humans. Probably, a genetic variant of adenosine deaminase, which is associated with the reduced metabolism of adenosine to inosine, specifically enhances deep sleep and slow wave activity during sleep. Thus low activity of the catabolic enzyme for adenosine results in elevated adenosine, and deep sleep. In contrast, insomnia patients could have a distinct polymorphism of more active adenosine deaminase resulting in less adenosine accumulation, insomnia, and a low threshold for anxiety. This could also explain interindividual differences in anxiety symptoms after caffeine intake in healthy volunteers. This could affect the EEG during sleep and wakefulness in a non-state-specific manner. 

Viruses lack independent metabolism. They multiply only inside living cells, using the host cell metabolic machinery. Some virus particles do contain enzymes, however, that are under the genetic control of the virus genome. Such enzymes are only produced during the infection cycle. 

This feat of "accelerated microevolution" involved the genetically controlled production of a dehydrochlorinating enzyme ("DDT-ase") that converted DDT to DDE. Microsomal oxidation of the latter produced polar degradable compounds. 

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