Acetylation coenzyme A for

Abbreviation for acetyl coenzyme A (for complete stmcture see Figure 26 1)... 

The form in which acetate is used in most of its important biochemical reactions is acetyl coenzyme A (Figure 26 la) Acetyl coenzyme A is a thwester (Section 20 13) Its for matron from pyruvate involves several steps and is summarized m the overall equation... 

We can descnbe the major elements of fatty acid biosynthesis by considering the for mation 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 referred to as acyl carrier protein (ACP), bear a side chain that is structurally similar to coenzyme A An important early step m fatty acid biosynthesis is the transfer of the acetyl group from a molecule of acetyl coenzyme A to the sulfhydryl group of acyl carrier protein... 

The neurotransmitter must be present in presynaptic nerve terminals and the precursors and enzymes necessary for its synthesis must be present in the neuron. For example, ACh is stored in vesicles specifically in cholinergic nerve terminals. It is synthesized from choline and acetyl-coenzyme A (acetyl-CoA) by the enzyme, choline acetyltransferase. Choline is taken up by a high affinity transporter specific to cholinergic nerve terminals. Choline uptake appears to be the rate-limiting step in ACh synthesis, and is regulated to keep pace with demands for the neurotransmitter. Dopamine [51 -61-6] (2) is synthesized from tyrosine by tyrosine hydroxylase, which converts tyrosine to L-dopa (3,4-dihydroxy-L-phenylalanine) (3), and dopa decarboxylase, which converts L-dopa to dopamine. 

The four car bon atoms of the butanoyl group originate in two molecules of acetyl coenzyme A. Carbon dioxide assists the reaction but is not incorporated into the product. The sfflne car bon dioxide that is used to convert one molecule of acetyl coenzyme A to malonyl coenzyme A is regenerated in the decarboxylation step that accompanies carbon-carbon bond for-mation. 

Would you expect the free energy of hydrolysis of aceto-acetyl-coenzyme A (see diagram) to be greater than, equal to, or less than that of acetyl-coenzyme A Provide a chemical rationale for your answer. 

Breeze A.S. Simpson A.M. (1982) An improved method using acetyl-coenzyme A regeneration for the enzymic inactivation of aminoglycosides prior to sterility testing. JApplBacteriol, 53, 277-284. 

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. 

Chee-Sanford JC, JW Frost, MR Fries, Z Zhou, JM Tiedje (1996) Evidence for acetyl coenzyme A and cin-namoyl coenzyme A in the anaerobic toluene mineralization pathway in Azoarcus tolulyticus Tol-4. Appl Environ Microbiol 62 964-873. 

Mononuclear Ni complexes have been investigated as functional models for individual steps of the reactions mediated by the CODH/acetyl coenzyme A synthase.2018-2020 These are mentioned in the respective sections on mononuclear Ni complexes. The dinuclear type (770) complexes are... 

Acetylcholine synthesis and neurotransmission requires normal functioning of two active transport mechanisms. Choline acetyltransferase (ChAT) is the enzyme responsible for ACh synthesis from the precursor molecules acetyl coenzyme A and choline. ChAT is the neurochemical phenotype used to define cholinergic neurons although ChAT is present in cell bodies, it is concentrated in cholinergic terminals. The ability of ChAT to produce ACh is critically dependent on an adequate level of choline. Cholinergic neurons possess a high-affinity choline uptake mechanism referred to as the choline transporter (ChT in Fig. 5.1). The choline transporter can be blocked by the molecule hemicholinium-3. Blockade of the choline transporter by hemicholinium-3 decreases ACh release,... 

Lopez JM, Bennett MK, Sanchez HB, Rosenfeld JM, Osborne TE. Sterol regulation of acetyl coenzyme A carboxylase a mechanism for coordinate control of cellular lipid. Proc Natl Acad Sci USA 1996 93 1049-1053. 

Brain ChAT has a KD for choline of approximately 1 mmol/1 and for acetyl coenzyme A (CoA) of approximately 10pmol/l. The activity of the isolated enzyme, assayed in the presence of optimal concentrations of cofactors and substrates, appears far greater than the rate at which choline is converted to ACh in vivo. This suggests that the activity of ChAT is repressed in vivo. Surprisingly, inhibitors of ChAT do not decrease ACh synthesis when used in vivo this may reflect a failure to achieve a sufficient local concentration of inhibitor, but also suggests that this step is not rate-limiting in the synthesis of ACh [18-20]. 

Acetyl coenzyme A formed from glucose is the precursor for acetylcholine 543... 

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