Acetyl coenzymeA

Histone acetyltransferases (HATs) are enzymes that acetylate specific lysine residues in histones through the transfer of an acetyl group from an acetyl-coenzymeA (AcCoA) molecule, causing profound effects on chromatin structure and assembly as well as gene transcription. HATs are found in most, if not all, eukaryotic organisms as multiprotein complexes, some HAT catalytic subunits even being shared between various complexes that display different substrate specificities based on their subunit composition [12]. Despite their name, HATs do not restrict themselves to the acetylation of histones, since these enzymes have also been shown to act on nonhistone proteins, broadening their scope of action [13]. 

A familiar example of this type of metabolite adaptation is the thiol ester derivative of acetic acid, acetyl-coenzymeA (acetylCoA). AcetylCoA has a much larger negative free energy of hydrolysis than acetate, so metabolic transformations involving the acetate ion can occur with much lower concentrations of acetylCoA than of acetate. Phosphorylated metabolic intermediates likewise allow metabolites to have high chemical potentials and occur at relatively low concentrations in the cellular water. Use of such activated intermediates enables the cell to avoid high concentrations of metabolites that can tax solvent capacity and, perhaps more important, disrupt the cell through uncontrolled chemical reactions with inappropriate molecules. 

Bakg + Bqaa- Abbreviations T, activity of the citric acid dele P, activity of the oxidative pentose phosphate pathway Glc6P, glucose 6-phosphate Fru6P, fructose-6-phosphate Gra3P, glyceraldehyde 3-phosphate PEP, phosphoenolpyruvate PYR, pyruvate AcCoA, acetyl coenzymeA OAA, oxaloacetate, AKG, 2-oxoglutarate... 

Athappilly FK, Hendrickson WA (1995) Structure of the biotinyl domain of acetyl-coenzymeA carboxylase determined by MAD phasing. Structure 3 1407-19... 

SCoA SCoA acetyl-CoenzymeA aoetyl-CoenzymeA... 

Fig. 14. Proposed pathway of maltose and of pyruvate fermentation to acetate, H2 and CO2 in Pyrococcus furiosus. Fdox, oxidized ferredoxin Fdred, reduced ferredoxin CoA, coenzymeA. Numbers in circles refer to enzymes involved (1) Q-glucosidase [296] (2) glucoserferredoxin oxidoreductase (3) gluconate dehydratase (this enzyme has not been detected so far in Pyrococcus furiosus) (4) 2-keto-3-deoxygluconate aldolase (5) glyceraldehyde ferredoxin oxidoreductase (6) glycerate kinase (2-phosphoglycerate forming) (7) enolase (8) pyruvate kinase (9) pyruvateiferredoxin oxidoreductase (10) ADP-forming acetyl-CoA synthetase (11)...

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