Coenzyme A CoA

This coenzyme is composed of adenine, ribose, phosphate and a chain formed by amide links between one hydroxy acid, one amino acid and thioethanolamine. The chemical role of CoA is derived from the thiol 

---

Zn-+ DNA polymerase Coenzyme A (CoA) Acyl groups Acetyl-CoA carboxylase... 

Pantothenic acid, sometimes called vitamin B3, is a vitamin that makes up one part of a complex coenzyme called coenzyme A (CoA) (Figure 18.23). Pantothenic acid is also a constituent of acyl carrier proteins. Coenzyme A consists of 3, 5 -adenosine bisphosphate joined to 4-phosphopantetheine in a phosphoric anhydride linkage. Phosphopantetheine in turn consists of three parts /3-mercaptoethylamine linked to /3-alanine, which makes an amide bond with a branched-chain dihydroxy acid. As was the case for the nicotinamide and flavin coenzymes, the adenine nucleotide moiety of CoA acts as a recognition site, increasing the affinity and specificity of CoA binding to its enzymes. 

Figure 21.9 Formation of the thioester acetyl CoA by nucleophilic acyl substitution reaction of coenzyme A (CoA with acetyl adenylate.

The sharp flash in the firefly bioluminescence reaction (Fig. 1.6) is due to the formation of a strongly inhibitory byproduct in the reaction. The inhibitor formed is dehydroluciferyl adenylate, having the structure shown below at left. In the presence of coenzyme A (CoA), however, this inhibitory adenylate is converted into dehydroluciferyl-CoA, a compound only weakly inhibitory to luminescence. Thus, an addition of CoA in the reaction medium results in a long-lasting, high level of luminescence (Airth et al., 1958 McElroy and Seliger, 1966 Ford et al., 1995 Fontes et al., 1997, 1998). 

Pantothenic acid is an essential component of coenzyme A (CoA) (Fig. 2) and - as pantetheine - of fatty acid synthase. The HS-group of cysteamine is... 

Uchicda, Y., Izai, K., Orii, T., Hashimoto, T. (1992). Novel fatty acid p-oxidation enzymes in rat liver mitochondria. II. Purification and properties of enoyl-coenzyme A (CoA) hydratase/3-hy-droxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase trifunctional protein. J. Biol. Chem. 267, 1034-1041. 

Lochmeyer C, 1 Koch, G Fuchs (1992) Anaerobic degradation of 2-aminohenzoic acid (anthranilic acid) via henzoyl-coenzyme A (CoA) and cyclohex-l-enecarhoxyl-CoA in a denitrifying bacterium. J Bacteriol 174 3621-3628. 

CLC Charcot-Leyden crystal CMC Critical micellar concentration CMI Cell mediated immunity CML Chronic myeloid leukaemia CMV Cytomegalovirus CNS Central nervous system CO Cyclooxygenase CoA Coenzyme A CoA-IT Coenzyme A - independent transacylase... 

Many substances which are necessary (and even essential) for life functions contain sulphur for example, the amino acids cysteine and methionine, the tripeptide glutathione or coenzyme A (CoA), with the latter containing the SH group of cys-teamine as the terminal functional group. CoA acts as a coenzyme in all important biochemical acylations. The cysteamine SH group bonds to carboxylic acids to give thioesters ... 

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]. 

Structures of CHS complexed with different Coenzyme A (CoA) thioesters and product analogs (i.e., naringenin and resveratrol) demonstrate that the active site is buried within an interior cavity located in the cleft between the upper and lower domains of each monomer (Fig. 12.3). Considering the complexity of the reaction... 

Coenzyme A (CoA), 20 249—250. See also Ace to acetyl- Co A in citric acid cycle, 6 633 Coenzyme Q10, 17 673 Coercivity, ofM-type ferrites, 11 70 Coextruded food packaging, 18 44, 45 Coextrusion techniques, for gelatin capsule preparation, 11 549 Cofactors, 10 253 11 4 folic acid, 25 801-802 for enzymes, 3 672-673 protein, 20 828-829 vitamin B12, 25 804 vitamins as, 25 781 Coffea arabica, 7 250 Cojfea Canephora, 7 250 Coffea liberica, 7 250 Coffee, 2 108 6 366 7 250-271 biotechnology, 7 265-267 decaffeinated, 7 263 economic aspects, 7 263-264 estimated maximum oxygen tolerance, 3 381t... 

Isobutyryl-coenzyme A (CoA) dehydrogenase deficiency (IBD deficiency) is a rare disorder in which the body is unable to process certain proteins properly. People with this disorder have inadequate levels of an enzyme that helps break down the amino acid valine, a building block of proteins. 

Mammalian HAT enzymes can be divided into subfamilies (Tan, 2001). However, it is currently difficult to classify a protein as a potential HAT enzyme based on its amino acid sequence, since these subfamilies display no obvious similarity in their primary sequence, nor in the size of their HAT domains or the surrounding protein modules (Kuo and Allis, 1998 Marmorstein, 2001). The only region that is partly conserved between HAT subfamilies, either on the amino acid sequence and/or structural level, is a small subdomain first noticed in GCN5-related N-acetyltransferases, which encompasses the coenzyme A (CoA) binding site (Neuwald and Landsman, 1997 Martinez-Balbas et al, 1998 Yan et al, 2000 Marmorstein and Roth, 2001). Four families of mammalian HATs that have been implicated in human disease will be discussed here. 

When fatty adds are used in metabolism, they are first activated by attaching coenzyme A (CoA) fatty acyl CoA synthetase catalyzes this activation step. The product is genetically referred to as a fatty acyl CoA or sometimes just acyl CoA. Specific examples would be acetyl CoA with a 2-carbon acyl group, or palmitoyl CoA with a 16-carbon acyl group. 

Fig. 7. Enzyme-coupled assay in which the hydrolase-catalyzed reaction releases acetic acid. The latter is converted by acetyl-CoA synthetase (ACS) into acetyl-CoA in the presence of (ATP) and coenzyme A (CoA). Citrate synthase (CS) catalyzes the reaction between acetyl-CoA and oxaloacetate to give citrate. The oxaloacetate required for this reaction is formed from L-malate and NAD in the presence of L-malate dehydrogenase (l-MDH). Initial rates of acetic acid formation can thus be determined by the increase in adsorption at 340 nm due to the increase in NADH concentration. Use of optically pure (Ry- or (5)-acetates allows the determination of the apparent enantioselectivity i app i81)-...

The synthetic form is the alcohol, panthenol, which can be oxidized in vivo to pantothenic acid. It is included in the list of substances that may be added in foods and in food supplements [403], Pantothenic acid is part of the coenzyme A (CoA) molecule therefore it is involved in acylation reactions, such as in fatty acid and carbohydrate metabolism. 

Most fuel molecules enter the pathway as acetyl coenzyme A (CoA), but the carbon skeletons of the amino acids may also enter the TCA cycle at various points. 

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. 

---