Acetyl coenzyme A, formation

Acetyl coenzyme A, formation, 45 Achlya, sterol utilization, 318,321 Aohlya ambisexualis. growth inhibition, 337 Achlya carolinlana. growth inhibition, 337... 

Grumbach K. and Forn B. 1980. Chloroplast autonomy in acetyl-coenzyme-A formation and terpenoid biosynthesis. Z. Naturforsch. 35c, 645-648. 

The four carbon atoms of the butanoyl group originate m two molecules of acetyl coenzyme A Carbon dioxide assists the reaction but is not incorporated into the prod uct The same carbon dioxide that is used to convert one molecule of acetyl coenzyme A to malonyl coenzyme A is regenerated m the decarboxylation step that accompanies carbon-carbon bond formation... 

Carbon-carbon bond formation then occurs between the ketone carbonyl of acetoacetyl coenzyme A and the a carbon of a molecule of acetyl coenzyme A... 

The fonn in which acetate is used in most of its important biochemical reactions is acetyl coenzyme A (Figure 26.1a). Acetyl coenzyme A is a thioester (Section 20.13). Its formation from pyruvate involves several steps and is summarized in the overall equation ... 

We can describe the major elements of fatty acid biosynthesis by considering the formation of butanoic acid from two molecules of acetyl coenzyme A. The machinery responsible for accomplishing this conversion is a complex of enzymes known as fatty acid synthetase. Certain portions of this complex, refened to as acyl carrier protein (ACP), bear a side chain that is structurally similar to coenzyme A. An important early step in fatty acid biosynthesis is the transfer of the acetyl group from a molecule of acetyl coenzyme A to the sulfhydryl group of acyl canier protein. 

The acetyl-coenzyme A decarbonylase synthase complex contains five polypeptide sub-nnits and in acetate-degrading methanotrophs, such as Methanosarcina barkeri and M. thermophila, catalyzes the formation of methane and COj from acetyl-CoA ... 

The degradation of vinyl chloride and ethene has been examined in Mycobacterium sp. strain JS 60 (Coleman and Spain 2003) and in Nocardioides sp. strain JS614 (Mattes et al. 2005). For both substrates, the initially formed epoxides underwent reaction with reduced coenzyme M and, after dehydrogenation and formation of the coenzyme A esters, reductive loss of coenzyme M acetate resulted in the production of 5-acetyl-coenzyme A. The reductive fission is formally analogous to that in the glutathione-mediated reaction. 

Gould and coworkers have extensively studied the biosyntheses of the kinamycins, and this work was recently reviewed [5a]. Feeding studies established that the carbo-cyclic skeletons of the kinamycins are constructed from 10 equivalents of 5-acetyl coenzyme A, and the pathway shown in Scheme 3.4 was proposed. The pathway begins with formation of the natural product dehydrorabelomycin (29). A novel ring contraction then occurs to form the cyclopentadienone 30. Feeding studies with /V-15-ammonium sulfate established that the diazo functional group is then installed... 

The role of N-acetoxy arylamides as metabolically formed ultimate carcinogens jji vivo also appears to be limited. Their enzymatic formation via peroxidation of N-hydroxy arylamides can be excluded since tissues containing high levels of peroxidases such as the rat mammary gland (83) and the dog urinary bladder (84) do not form acetylated carcinogen-DNA adducts in vivo (63). Their non-enzymatic formation by reaction of acetyl coenzyme A with N-hydroxy arylamides (6 ) cannot be excluded however, even if formed, their direct reaction with cellular DNA appears unlikely as treatment of cultured cells with synthetic N-acetoxy AAF (85,86) results primarily in deacetylated arylamine-DNA adducts, apparently due to rapid N-deacetylation to form the reactive N-acetoxy arylamine (V). 

As the principal thiolester of intermediary metabolism, acetyl coenzyme A is involved in two-carbon biosynthetic and degradative steps. An essential component is the vitamin pantithenic acid, which provides the sulfur atom for the thiolester formation. 

Selected entries from Methods in Enzymology [vol, page(s)] Assay, 1, 611 3, 935-938 63, 33 separation by HPLC, 72, 45 extraction from tissues, 13, 439 formation of, 1, 486, 518, 585 5, 466 free energy of hydrolysis, 1, 694 substrate for the following enzymes [acetyl-coenzyme A acyl carrier protein transacylase, 14, 50 acetyl-coenzyme A carboxylase, 14, 3, 9 acetyl-coenzyme A synthetase, 13, 375 N-acetyltransferase, 17B, 805 aminoacetone... 

Biotin (vitamin B ) is widespread in foods and is also synthesized by intestinal bacteria. It is a coenzyme for the carboxylation of pyruvate, acetyl-coenzyme-A (CoA), propionyl CoA, and /1-methyl-crotonyl CoA and is involved in fatty acid formation and in energy release from carbohydrates. In humans deficiencies only occur in patients with an abnormal gut flora and manifests itself as exfoliative dermatitis and alopecia. 

S ATP -P acetate <1-18> (<8> acetate kinase/phosphotransacetylase, major role of this two-enzyme sequence is to provide acetyl coenzyme A which may participate in fatty acid synthesis, citrate formation and subsequent oxidation [1] <3> function in the metabolism of pyruvate or synthesis of acetyl-CoA coupling with phosphoacetyltransacetylase [15] <11> function in the initial activation of acetate for conversion to methane and CO2 [19] <10> key enzyme and responsible for dephosphorylation of acetyl phosphate with the concomitant production of acetate and ATP [30]) (Reversibility r <1-18> [1, 2, 5-21, 24-27, 29-33]) [1, 2, 5-21, 24-27, 29-33]... 

Acetamidodeoxyhexoses. A further modification of the 4-keto-inter-mediate has been independently shown by Ashwell and by Strominger and associates (Table I, References 20, 21, 22, 23). Transamination reactions with L-glutamate as the amino donor and pyridoxal phosphate as coenzyme led to formation of 3-amino 3,6-dideoxy- and 4-amino 4,6-dideoxyhexoses, respectively. Acetylation with acetyl coenzyme A yields the naturally-occurring N-acetyl amino sugar derivatives. 

Lewisite is the most important of the organo-arseni-cal CW agents. Exposure to lewisite is quite painful, and onset of symptoms occurs rapidly (seconds to minutes) (31) in contrast to sulfur mustard for which a latency period occurs of several hours between exposure and symptoms (32). Although it is not known to have been used as a CW agent, lewisite is still considered a potential threat due to the relative ease of production and its rapid onset of action. Moreover, substantial stockpiles of lewisite are present in the United States, Russia, and in China abandoned by the Japanese Imperial Army. This may constitute a potential hazard for public health (33). The toxicity of lewisite is inter alia caused by the high affinity for the vicinal di-thiol system present in dihydrolipoic acid, a component of the pyruvate dehydrogenase complex, as is the case for other arsenicals (34). This prevents the formation of acetyl coenzyme A from pyruvate. 

Practically all tissues can degrade glucose by the process of glycolysis. In this pathway, glucose is converted to two molecules of pyruvate, with the production of two ATP molecules. Two molecules of NAD+ are also reduced to NADH. Pyruvate may proceed in at least two directions toward the formation of lactate, in which case the glycolysis is anaerobic, or toward the formation of acetyl coenzyme A (acetyl-CoA) and oxidation via the Krebs cycle (also called the tricarboxylic acid cycle). In the former case, pyruvate is reduced by NADH and... 

Conversion of (S)-reticuline to its ( )-epimer is the first committed step in morphinan alkaloid biosynthesis in certain species. 1,2-Dehydroreticuline reductase catalyzes the stereospecific reduction of 1,2-dehydroreticuline to (7 )-reticuline.39 Intramolecular carbon-carbon phenol coupling of (if)-reticuline by the P450-dependent enzyme salutaridine synthase (STS) results in the formation of salutaridine.40 The cytosolic enzyme, salutaridine NADPH 7-oxidoreductase (SOR), found in Papaver bracteatum and P. somniferum, reduces salutaridine to (7S)-salutaridinol.41 Conversion of (7S)-salutaridinol into thebaine requires closure of an oxide bridge between C-4 and C-5 by acetyl coenzyme A salutaridinol-7-0-acetyltransferase (SAT). The enzyme was purified from opium poppy cultures and the corresponding gene recently isolated (Fig.7.2).42,43 In the last steps of morphine... 

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