Pyruvate oxidation factor

The isolation of lipoic acid in 1951 followed an earlier discovery that the ciliate protozoan Tetrahymena geleii required an unknown factor for growth. In independent experiments acetic acid was observed to promote rapid growth of Lactobacillus casei, but it could be replaced by an unknown "acetate replacing factor." Another lactic acid bacterium Streptococcus faecalis was unable to oxidize pyruvate without addition of "pyruvate oxidation factor." By 1949, all three unknown substances were recognized as identical.291 2913 After working up the equivalent of 10 tons of water-soluble residue from liver, Lester Reed and his collaborators isolated 30 mg of a fat-soluble acidic material which was named lipoic acid (or 6-thioctic acid).292 294... 

Gunsalus, I. C. The chemistry and function of the pyruvate oxidation factor (lipoic acid). J. Cellular Comp. Physiol. 41, Suppl. 1, 113—136 (1953). 

Lipoic Acid. The formation of acetyl CoA from pyruvate involves an additional cofactor, lipoic acid. This compound was studied independently as a growth factor for the protozoa Tetrahymena (protogen), a growth factor for Lactobacillus casei (acetate replacing factor) and a pyruvate oxidation factor for Streptococcus faecalis. - Pure synthetic compounds were made and called thioctic acid and lipoic acid. The officially accepted name for the structure given below is lipoic acid. Lipoic acid is... 

Pyruvate oxidation factor has been identified as a-lipoic acid,... 

Thiamine pyrophosphate (TPP) is the active form of thiamine in the cells of all organisms and, as such, is important as a coenzyme in the decarboxylation of a-keto acids, as well as in the biosynthesis of certain acyloins. In view of the recent findings of Reed and De Busk (see section on pyruvate oxidation factor) TPP may form a complex with a-lipoic acid, which may be the coenzyme for the oxidative decarboxylation of a-keto acids. 

It is of interest to note that the thiol form of TPP contains the j3-thiol-ethylamine configuration present in coenzyme A. The fact that glutathione, coenzyme A, and the pyruvate oxidation factor all are sulfur-containing compounds is highly suggestive of the possibility that TPP is also active in the thiol form. Cavallini has recently shown that in vitro at pH 7.4, the oxidation of GSH by oxygen in the presence of traces of copper or cytochrome c may be coupled with a simultaneous oxidation of pyruvate to acetate and CO2. The reaction probably depends on the intermediate formation of a GSH-pyruvate complex and is suggested as a possible model for the action of TPP. 

Schweet et al have reported the partial purification of a soluble pyruvic oxidase from pigeon breast muscle that converts pyruvate to to acetate and CO2. The preparation contains flavin and protogen (pyruvate oxidation factor). Cocarboxylase and Mg++ are required for full activity. It is reported that CoA, DPN, or TPN are not required. 

Somewhat later O Kane and Gunsalus observed that, when Streptococcus faecalis was grown in a synthetic medium, the harvested cells were unable to oxidize pyruvic acid unless supplemented with yeast extract or other natural materials. The activity of yeast extract could not be replaced by any of the known coenzymes or vitamins. The name pyruvate oxidation factor (POF) was therefore used to designate the biological activity of this factor. 

An application of the same procedure to pyruvate, building on data from Kay Miller s thesis, led Dan O Kane to an additional requirement for pyruvate oxidation we termed pof, pyruvate oxidation factor. Recognized as an unidentified substance, the next decade led us to the isolation, synthesis and understanding of energy coupling in keto acid oxidation. 

The blocked-out purification of pyruvate oxidation factor was taken with us to Indiana and the early steps were scaled up for us at the Eli Lilly Research Laboratories in Indianapolis. Later, at the time of my transfer to Illinois, a realignment of the LUly research mana ment revealed to them the identity of the pyruvate oxidation and the acetate replacing factors, the latter supplied to Lester Reed at Texas. A pointed encouragement came from Lilly for us to join forces, which we did, continuing with the best features from each effort. ... 

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