Pyruvate anaerobic conditions

Incorrect - The two pathways are alternative pathways for converting carbohydrate to pyruvate, and are found in various organisms. They operate in aerobic or anaerobic conditions. 

Lactate is the end product of glycolysis under anaerobic conditions (eg, in exercising muscle) or when the metabolic machinery is absent for the further oxidation of pyruvate (eg, in erythrocytes). 

Attention is drawn to the dechlorination by anaerobic bacteria of both chlorinated ethenes and chlorophenolic compounds that serve as electron acceptors with electron donors including formate, pyruvate, and acetate. This is termed dehalorespiration and is important in the degradation of a range of halogenated compounds under anaerobic conditions, and is discussed further in Chapter 3, Part 2 and Chapter 7, Part 3. 

Earlier studies showed that reactions of sugars with ammonia lead to small molecules such as amines or organic acids. A. L. Weber has reported important autocatalytic processes occurring when trioses are allowed to react with ammonia under anaerobic conditions, such reactions provide products which are autocatalyt-ically active. Their autocatalytic activity was determined directly by investigating their effect on an identical triose-ammonia reaction. Both an increase in the triose degradation rate and an increased rate of synthesis of pyruvate, the dehydration product of the triose, were observed. Such processes may have been of importance for prebiotic chemistry occurring on the primeval Earth (Weber, 2007). 

By the beginning of October that year results from Johnson s experiments allowed Krebs to report at a Biochemical Society meeting in Cambridge If pyruvic acid is added to tissues under anaerobic conditions, together with malic acid or oxaloacetic acid, very considerable quantities of citric acid are formed. ... 

The glycolytic pathway, or glycolysis, is a metabolic sequence in which glucose is broken down to pyruvic acid. The subsequent fate of pyruvate then depends upon whether or not the organism is aerobic or anaerobic Under aerobic conditions, pyruvate is oxidized via oxidative phosphorylation under anaerobic conditions, pyruvate is converted further into compounds such as lactate or ethanol, depending upon the organism. 

C. In cells that are unable to transfer electrons to oxygen due to lack of mitochondria, eg, RBCs, or in vigorously exercising muscle cells (anaerobic conditions), NAD" is regenerated by further metabolism of pyruvate. 

The only metabolic activity that has been for decades ascribed to the trichomonad hydrogenosome was related to energy metabolism. It has been unequivocally shown that, under anaerobic conditions, isolated intact hydrogenosomes produced roughly equimolar amounts of acetate, CO2, and hydrogen from pyruvate in a process accompanied by substrate-level phos-... 

Fates of Pyruvate under Anaerobic Conditions Fermentation 538... 

The third major route of pyruvate catabolism leads to ethanol. In some plant tissues and in certain invertebrates, protists, and microorganisms such as brewer s yeast, pyruvate is converted under hypoxic or anaerobic conditions into ethanol and C02, a process called ethanol (alcohol) fermentation (Fig. 14-3). 

The product of this metabolic sequence, pyruvate, is a metabolite of caitral importance. Its fate depends upon the conditions within a cell and upon the type of cell. When oxygen is plentiful pyruvate is usually converted to acetyl-coenzyme A, but under anaerobic conditions it may be reduced by NADH + H+ to the alcohol lactic acid (Fig. 10-3, step h). This reduction exactly balances the previous oxidation step, that is, the oxidation of glycer-aldehyde 3-phosphate to 3-phospho-glycerate (steps a and b). With a balanced sequence of an oxidation reaction, followed by a reduction reaction, glucose can be converted to lactate in the absence of oxygen, a fermentation process. The lactic acid fermentation occurs not only in certain bacteria but also in our own muscles under conditions of extremely vigorous exercise. It also occurs continuously in some tissues, e.g., the transparent lens and cornea of the eye. 

Experimental support for the mechanism of Eq. 15-26 has been obtained using D-chloroalanine as a substrate for D-amino acid oxidase.252-254 Chloro-pyruvate is the expected product, but under anaerobic conditions pyruvate was formed. Kinetic data obtained with a-2H and a-3H substrates suggested a common intermediate for formation of both pyruvate and chloro-pyruvate. This intermediate could be an anion formed by loss of H+ either from alanine or from a C-4a adduct. The anion could eliminate chloride ion as indicated by the dashed arrows in the following structure. This would lead to formation of pyruvate without reduction of the flavin. Alternatively, the electrons from the carbanion could flow into the flavin (green arrows), reducing it as in Eq. 15-26. A similar mechanism has been suggested for other flavoenzymes 249/255 Objections to the carbanion mechanism are the expected... 

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