Propionic acid racemase

Also other members of the profen-family, among them naproxen, flurbiprofen, ketoprofen and tiaprofenic acid, are of great importance today. In general, these are 2-aryl- or 2-heteroaryl-propionic acids, of which in vitro only the (S)-(+)-enantiomer inhibits cyclooxygenase-1 (Fig. 5.84). In vivo, depending on the particular animal species, and also in humans, the (U)-(-)-enantiomer is converted to various degrees into its (S)-enantiomer with the aid of -methylacyl-CoA-racemase, via the Coenzyme A-thioester. In addition, more recent investigations could show that (R)-ibuprofen and (R)-flurbiprofen themselves have also anti-inflammatory properties. Many of the profens, with the exception of naproxen, are therefore marketed as racemates. 

Methylmalonyl-CoA racemase. The enzyme catalyzes the transformation of the isomer (b) of methylmalonyl-CoA to the isomer (a), which can be used at subsequent steps of propionic acid fermentation ... 

The propionate oxidase can be obtained as a saline extract from acetone-dried, washed liver cyclophorase preparation. This enzyme is very labile and loses its activity within several hours after its preparation even at 5 C. or in the frozen state. The material called a-hydroxy acid racemase is found in the first supernatant fluid of cyclophorase preparations of either liver or kidney. The active substance appears to be a protein fairly stable to elevated temperatures, repeated freezing and thawing, and precipitation by acetone and alcohol. 

Mazumder, R., Sasakawa, T., Kaziro, Y. and Ochoa, S. (1962), Metabolism of propionic acid in animal tissues. IX. Methylmalonyl CoA racemase. J. Biol. Chem., 372, 3065. 

Fermentation of glucose, glycerol, and lactic acid by propionibacteria utilizing the succinate-propionate pathway. 1 (S)-methylmalonyl-CoA-pyruvate transcarboxylase, 2 malate dehydrogenase 3 fumarase, 4 fumarate reductase, 5 CoA transferase, 6 (R)-methylmalonyl-CoA mutase, and 7 methylmalonyl-CoA racemase... 

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