CoA, coenzyme

Fig. 11. Active sites and reactions of the bifunctional CODH/ACS. For synthesis of acetyl-CoA, two electrons are transferred from external electron donors to Cluster B of the CODH subunit. Electrons are relayed to Cluster C which reduces CO2 to CO. The CO is proposed to be channeled to Cluster A of the ACS subunit to form a metal-CO adduct that combines with the methyl group of the CFeSP and CoA to form acetyl-CoA. For utilization of acetyl-CoA, these reactions are reversed. The abbreviations are CODH, CO dehydrogenase ACS, acetyl-CoA synthase CFeSP, the corrinoid iron-sulfur protein CoA, Coenzyme A.

The citric acid cycle is an integral part of the process by which much of the free energy liberated during the oxidation of fuels is made available. During oxidation of acetyl-CoA, coenzymes are reduced and subsequendy reoxidized in the respiratory chain, hnked to the formation of ATP (oxicktive phosphorylation see Figure 16-2 and also Chapter 12). This process is aerobic, requiring oxygen as the final oxidant of the reduced coenzymes. The enzymes of the citric acid cycle are lo-... 

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... 

Biochemical findings are variable. The blood cobala-min and folate levels often are normal. Patients often have homocysteinemia with hypomethioninemia, the latter finding discriminating this group from homocystinuria secondary to cystathionine- P-synthase deficiency. Urinary excretion of methylmalonic acid may be high, reflecting the fact that vitamin B12 serves as a cofactor for the methyl-malonyl-CoA (coenzyme A) mutase reaction. 

Figure 7-1. Conversion of pyruvate to acetyl CoA by the pyruvate dehydrogenase complex. The three enzymes, pyruvate dehydrogenase, dihydrolipoyl transacetylase, and dihydrolipoyl dehydrogenase, exist in a complex associated with the mitochondrial matrix. Each enzyme requires at least one coenzyme that participates in the reaction. TPP, thiamine pyrophosphate Lip, lipoic acid CoA, coenzyme A.

FIGURE 16.3 Overview of the biosynthesis of (I) chalcones and (II) 6 -deoxychalcones. The sequential condensation of three molecules of malonyl-CoA (acetate pathway) and p-coumaroyl-CoA (shikimate pathway) is catalyzed by the enzyme chalcone synthase.The production of 6 -deoxychalcones is thought to involve an additional reduction step at the tri- or tetraketide level, catalyzed by polyketide reductase.The origin of the A-ring carbons derived from the acetate pathway is indicated in bold. CoA, coenzyme A. 

Fig. 4.3. Biosynthesis, structure, and degradation of the pheromones 4 and 5 of Linyphia triangularis and Linyphia tenuipalpis. ACP, acyl carrier protein CoA, coenzyme A.

The sex pheromone is interesting from a biosynthetic perspective (see Fig. 4.3) because it is closely connected with primary metabohsm. That is, the monomer 4 is an intermediate in fatty acid biosynthesis. Condensation of acetyl-ACP (8 ACP, acyl carrier protein) with malonyl-CoA (9 CoA, coenzyme A) yields acetoacyl-ACP (10). Enantioselective reduction with NADPH leads to (R)-3-hydroxybutyryl-ACP (11). Two units of this precursor could then be condensed to form the pheromone 5, which then degrades to 4 and 6 as described above. Alternatively, 4 can also be formed by direct hydrolysis of intermediate 11. 

Table 3.1.3 Pathologic acylglycine species detected by organic acid analysis. CoA coenzyme A, FAO fatty acid oxidation, ILE isoleucine, LEU Leucine, MCAD medium-chain acyl-CoA dehydrogenase, MET methionine,...

Fig.3.8.3 Oxygen uptake by intact (a) and digitonin-permeabilized (b) fibroblasts. I-V Respiratory chain complexes I-V, AcCoA acetylcoenzyme A, BSA bovine serum albumin, CCP carbonyl cyanide m-chlorophenylhydrazone, Cit citrate, CoA coenzyme A, CS citrate synthase, Dig digitonin, Fo FI the ATPase components, Fum fumarase, G3P glycerol-3-phosphate, im inner membrane, Mai malate, Malo malonate, MDH malate dehydrogenase, OAA oxaloacetate, om outer membrane, PDH pyruvate dehydrogenase, Pi inorganic phosphate, Pyr pyruvate, Q ubiquinone, Rot rotenone, Succ succinate, t time...

Fig. 5.1.1 Isoprenoid biosynthetic pathway. The enzyme mevalonate kinase (black solid bar) is deficient in patients affected with mevalonic aciduria and hyperimmunoglobulinemia D and periodic fever syndrome. -CoA -Coenzyme A, HMG-CoA 3-hydroxy-3-methyl-glutaryl-coenzyme A, -PP -pyrophosphate...

Figure 3.10 Uptake of blood constituents by the mammary gland CoA, coenzyme A G-3-P, glycerol-3-phosphate FFA, free fatty acid FA, fatty acid TG, triglyceride, VLDL, very low density lipoprotein (from Hawke and Taylor, 1995).

Figure 13.3 Alternative pathways of pyruvate metabolism by homofer-mentative lactic streptococci. CoA = coenzyme A TPP = thiamine pyrophosphate. (Adapted from Thomas et at. 1979.)...

FIGURE 14.4 The metabolism and actions of acetylcholine (ACh). CoA = coenzyme A CHAT = choline acetylase. 

FIGURE 43.6 Amitriptyline has potent anticholinergic properties. CHAT = choline acetylase CoA = coenzyme A ACh = acetylcholine. 

Fig. 5.1. Fermentation pathways present in facultative anaerobic eukaryotes. Examples of fermentation pathways present in the cytosol and in subcellular compartments. Fermentation processes localized in hydrogenosomes (1-3) and mitochondria (4) are indicated by the shaded box. Examples of the anaerobic ATP-producing organelles shown can be found in trichomon-ads (1), chytridiomycete fungi (2), Nyctotherus ovalis (3), and parasitic helminths, bivalves and Euglena gracilis (4). CoA coenzyme A, DHAP dihydroxyacetone phosphate, Fd ferredoxin, Gly-3-P, glyceraldehyde-3-phosphate, PFO pyruvate ferredoxin oxidoreductase...

In addition, most peroxisomes catalyze the oxidation of long-chain fatty acids to acetyl CoA (coenzyme A), which can be transported through the cytosol to mitochondria for use in the tricarboxylic acid cycle. 

Figure 8.4. Pathways of tryptophan metaholism. Tryptophan dioxygenase, EC 1.13.11.11 formylkynurenine formamidase, EC 3.5.1.9 kynurenine hydroxylase, EC 1.14.13.9 kynureninase, EC 3.7.1.3 3-hydroxyanthranilate oxidase, EC 1.10.3.5 picolinate carboxylase, EC 4.1.1.45 kynurenine oxoglutarate aminotransferase, EC 2.6.1.7 kynurenine glyoxylate aminotransferase, 2.6.1.63 tryptophan hydroxylase, EC 1.14.16.4 and 5-hydroxytryptophan decarboxylase, EC 4.1.1.26. Relative molecular masses (Mr) tryptophan, 204.2 serotonin, 176.2 kynurenine, 208.2 3-hydroxykynurenine, 223.2 kynurenic acid, 189.2 xanthurenic acid, 205.2 and quinolinic acid 167.1. CoA, coenzyme A.

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