Pyruvate dehydrogenase complex nature

Lipoic acid (the other names are a-lipoic acid or thioctic acid) (Figure 29.9) is a natural compound, which presents in most kinds of cells. Lipoic acid (LA) is contained in many food products, in particular in meat, but it is also synthesized in human organism from fatty acids. Earlier, it has been shown that in humans lipoic acid functions as a component of the pyruvate dehydrogenase complex. However, later on, attention has been drawn to the possible antioxidant activity of the reduced form of lipoic acid, dihydrolipoic acid (DHLA) (Figure 29.9). 

Similarly, the pyruvate dehydrogenase complex (PDC) can be activated directly by electrogenerated methyl viologen radical cations (MV +) as mediator. Thus, the naturally PDC-catalyzed oxidative decarboxylation of pyruvic acid in the... 

Table 7-4. Naturally Occurring Compounds of Unproven Efficacy Administered Singly or in Combination to Patients with Pyruvate Dehydrogenase Complex (PDC) Deficiency ...

Perham, R. N., Duckworth, H. W. Roberts, G. C. K. (1981). Mobility of polypeptide chain in the pyruvate dehydrogenase complex revealed by proton NMR. Nature (London), 292,474-7. 

Similarly, the pyruvate (oxidase) dehydrogenase complex (PYOX) can be activated directly by electrogenerated methyl viologen radical cations (MV" ) as mediator. Thus, the naturally PYOX-catalyzed oxidative decarboxylation of pyruvic acid in the presence of coenzyme A (HSCoA) to give acetylcoenzyme A (acetyl-SCoA) (see section on oxidases) can be reversed. In this way, electroenzymatic reductive carboxylation of acetyl-SCoA is made possible (Fig. 15). 

This is not the only example of Nature inventing the assembly line a long time before Henry Ford — both pyruvate dehydrogenase and a-ketoglutarate dehydrogenase mentioned earlier in the chapter are also multi-enzyme complexes. 

Bates, D. L., Danson, M. J., Hale, G., Hooper, E. A., Peeham, R. N. (1977), Self-assembly and catalytic activity of the pyruvate dehydrogenase multienzyme complex of Escherichia coli, Nature 268, 313-316. 

LIpolc acid, 6-thioctic acid, (+)-S[3-(l,2-dithiola-nyl)j ptntanoic acid a coenzyme of hydrogen transfer and acyl group transfer reactions. L. a. is a component of the pyruvate dehydrogenase and the 2-oxo-glutarate dehydrogenase complexes (see Multienzyme complexes), which catalyse the oxidative decarboxylation of the corresponding 2-oxoacids (see also Tricarboxylic acid cycle). The natural form of L.a. is... 

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