Acetyl co-enzyme A

A decarboxylating, complex dehydrogenase Converts it to acetyl co-enzyme A. 

This soluble, cytosolic enzyme catalyses the 15 -0-acetylation of cardenolide tri- and tetrasaccharides. Using acetyl co-enzyme A as the acetyl donor, acetyl co-enzyme A digitoxin 15 -0-acetyltransferase (DAT) activity was detected... 

The condensation of acetyl co-enzyme A with oxaloacetic acid and the decarboxylation steps illustrate two of the general metabolic reactions of citric acid intermediates that play an important role in their utilization to form secondary metabolites. 

Glycolysis, catalysed by cytoplasmic enzymes, can operate under aerobic and anaerobic conditions to produce pyruvate, but in the absence of oxygen this is reduced further to ethanol, plus CO2 (or to lactic acid if no decarboxylation occurs). Anaerobic respiration (or fermentation) produces only two ATP molecules per molecule of glucose respired contrast this with six ATPs (though some authors claim eight ATPs) produced during pyruvate formation under aerobic conditions. In the presence of oxygen, further utilization of pyruvate occurs within the mitochondria. Here, oxidative decarboxylation of pyruvate to acetyl co-enzyme A (acetyl CoA), followed by complete oxidation of the... 

At this time, I was fortunate to have as collaborator Neil Madsen, who had recently come to spend a postdoctoral year in the Oxford Biochemistry Department after graduating from Carl Cori s Department in St. Louis, and who had chosen to risk possible disappointment by sharing with me the struggle with an apparently intractable problem. Neil had already succeeded in showing that acetate per se was not metabolized by extracts of our organisms but that such extracts were rich in acetate thiokinase activity and were thus able rapidly to form acetyl co-enzyme A from acetate, ATP and CoASH. However, despite all manner of tricks, we were unable to persuade such extracts either to oxidise acetate to CO2... 

Similar results have been obtained in a study of the biogenesis of vanillin (105) in Vanilla planifolia and a similar direct breakdown of the phenylpropanoid precursor ferulic acid (13) was proposed. The mechanism of breakdown of the cinnamic acids to Cg.Ci compounds has most reasonably been formulated by Zenk as a i -oxidation involving the removal of acetate (or more probably acetyl co-enzyme A) from the side chain of the phenylpropanoid substrate. A scheme based on these ideas is shown in Figure 5.11. 

Acetylation of amines is an important route for the metabolism of primary aromatic amines such as the sul-phonamide dmgs or the antituberculosis dmg isoniazid (Fig. 3.22). The co-factor involved in acetate transfer is acetyl co-enzyme A (acetyl CoA) and the reaction is catalysed by acetyl transferase, N-acetylation generally reduces toxicity. 

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