Enzyme, oxidative systems

Other Applications of Multi-Enzyme Oxidizing Systems... 

In a review by Bragdt et al. (2004) results and perspectives are given to change the salt-based oxidative systems for cleaner oxygen or hydrogen peroxide enzyme-based Tempo systems. Moreover, several immobilized Tempo systems have been developed [129]. 

The microsomal ethanol oxidizing system is another mechanism of ethanol metabolism. CYP2E1 may be an important enzyme in the metabolism of ethanol in heavy drinkers, who may have a 10-fold increase in activity. Two aUehc variants in the gene cl and c2) are associated with differing enzymatic activity. Approximately 40% of Japanese have the more active c2 allele, which is rare in individuals of European heritage (Sun et al. 2002). It is not believed to be a risk or protective factor in the development of alcohohsm, although current studies are examining its relationship to a variety of ethanol-related diseases. 

Carnitine (p-hydroxy-y-trimethylammonium butyrate), (CHjljN"—CH2—CH(OH)—CH2—COO , is widely distributed and is particularly abundant in muscle. Long-chain acyl-CoA (or FFA) will not penetrate the inner membrane of mitochondria. However, carnitine palmitoyltransferase-I, present in the outer mitochondrial membrane, converts long-chain acyl-CoA to acylcarnitine, which is able to penetrate the inner membrane and gain access to the P-oxidation system of enzymes (Figure 22-1). Carnitine-acylcar-nitine translocase acts as an inner membrane exchange transporter. Acylcarnitine is transported in, coupled with the transport out of one molecule of carnitine. The acylcarnitine then reacts with CoA, cat-... 

Aside from China, Japan, North Africa, and the Middle East, most tea is consumed as black tea, which is produced by promoting the enzymic oxidation of tea flavanols. For the production of green tea, inactivation of the tea enzyme system by rapid firing is carried out to prevent flavanol... 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Lynen had studied chemistry in Munich under Wieland his skill as a chemist led to the successful synthesis of a number of fatty acyl CoA derivatives which proved to be substrates in the catabolic pathway. Many of these C=0 or C=C compounds had characteristic UV absorption spectra so that enzyme reactions utilizing them could be followed spectrophotometrically. This technique was also used to identify and monitor the flavoprotein and pyridine nucleotide-dependent steps. Independent evidence for the pathway was provided by Barker, Stadtman and their colleagues using Clostridium kluyveri. Once the outline of the degradation had been proposed the individual steps of the reactions were analyzed very rapidly by Lynen, Green, and Ochoa s groups using in the main acetone-dried powders from mitochondria, which, when extracted with dilute salt solutions, contained all the enzymes of the fatty acid oxidation system. 

After the substrates containing either CH-OH or CH2-CH2 functional groups have been oxidized by the dehydrogenase enzyme-coenzyme system,... 

A further requirement for the development of a multi-enzyme oxidizing process would be the determination of the kinetic parameters of the enzymes and hence development of a model of the intended reaction system in terms of the relative productivities of the enzymes with respect to substrate conversion rates as well as electron transfer stoichiometry. 

The selective oxidation of alcohols to the corresponding aldehydes and ketones is of prime importance for organic synthesis, and various types of reagents have been described that achieve this transformation selectively and efficiently [141,142]. However, the number of sub-stoichiometric, nontoxic, non-hazardous oxidation systems has been relatively Umited. As copper enzymes such as galactose oxidase are known to catalyze this oxidation reaction, bioinspired homogeneous catalysts based on copper species have also been developed in recent years. 

The ability, evidenced by a variety of microorganisms (see Table VI) to activate molecular hydrogen and enable it to undergo oxidation and exchange reactions, has been attributed to an enzyme, or system of en-... 

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