Propionate tca cycle

Table 1. Oxidative pathways of glycolysis employed by various bacteria. Bacterium Embden-Meyerhof pathway Phosphoketolase (heterolactic) pathway Entner Doudoroff pathway Acetobacter aceti - + - Agrobacterium tumefaciens - - + Azotobacter vinelandii - - + Bacillus subtilis major minor - Escherichia coli + - - Lactobacillus acidophilus + - - Leuconostoc mesenteroides - + - Pseudomonas aeruginosa - - + Vibrio cholerae minor - major Zymomonas mobilis - - +

AB - High-resolution 13C . spectroscopy has been used to examine propionate metabolism in the perfused rat heart. A number of tricarboxylic acid (TCA) cycle intermediates are observable by 13C . in hearts perfused with mixtures of pyruvate and propionate. When the enriched 13C-labelled nucleus originates with pyruvate, the resonances of the intermediates appear as multiplets due to formation of multiply-enriched 13C-labelled isotopomers, whereas when the 13C-labelled nucleus originates with propionate, these same intermediates appear as singlets in the 13C spectrum since entry of propionate into the TCA cycle occurs via succinyl-CoA. An analysis of the isotopomer populations in hearts perfused with [3-13C]pyruvate plus unlabelled propionate indicates that about 27% of the total pyruvate pool available to the heart is derived directly from unlabelled propionate. This was substantiated by perfusing a heart for 2 h with [3-13C]-propionate as the only available exogenous substrate. Under these conditions, all of the propionate consumed by the heart, as measured by conventional chemical analysis, ultimately entered the oxidative pathway as [2-13C] or [3-13C]pyruvate. This is consistent with entry of propionate into the TCA cycle intermediate pools as succinyl-CoA and concomitant disposal of malate to pyruvate via the malic enzyme. 13C resonances arising from enriched methylmalonate and propionylcarnitine are also detected in hearts perfused with [3-13C] or [1-13C]propionate which suggests that 13C . may be useful as a non-invasive probe in vivo of metabolic abnormalities involving the propionate pathway, such as methylmalonic aciduria or propionic acidaemia.

In 1904, the German chemist Franz Knoop elucidated the steps in beta-oxidation by feeding dogs odd- and even-chain ω-phenyl fatty acids, such as ω-phenylvaleric acid and ω-phenylbutyric acid, respectively. The mechanism of beta-oxidation, . successive removal of two carbons, was realized when it was discovered that the odd-chain ω-phenylvaleric acid was metabolized to hippuric acid , and that the even-chain ω-phenylbutyric acid was metabolized to phenaceturic acid . At this time, any reaction mechanism involving oxidation at the beta carbon was as yet unknown in organic chemistry . [10] [11]

Propionate tca cycle

propionate tca cycle


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