6-Ketostearic acid

It has been reported that a microbial isolate, Flavobacterium sp. strain DS5, produced 10-ketostearic acid (10-KSA) from oleic acid in 85% yield (Hou, 1994a). The purified product was white, plate-like crystals melting at 79.2°C. A small amount of 10-hydroxystearic acid (10-HSA) was also produced during the bioconversion, suggesting that oleic acid is converted to 10-KSA via 10-HSA, and the enzyme catalyzing the hydration is C-10 positional specific (Hou, 1994b, 1995). The DS5 bioconversion products from oleic, linoleic, a-linolenic, and y-linolenic acid are all 10-hydroxy fatty acids. The optimum time, pH, and temperature for the production of 10-KSA have been reported in flask... 

Hou, C. T. 1994a. Production of 10-ketostearic acid from oleic acid by Flavobacterium sp. Strain DS5 (NRRL B-14859). Appl. Env. Microbiol., 60,3760-3763. 

Hou, C.T., Production of 10-Ketostearic Acid from Oleic Acid by a New Microbial Isolate, Flavobacterium sp. (NRRL B-14859), Appl. Environ. Microbiol. 60 3760—3763 (1994). 

Wallen et al. described the hydration of oleic acid to hydroxystearic acid by a Pseudomonas strain 3266 already in the 1960s (Davis et al. 1969). Several bacterial strains have been isolated that are able to hydrate oleic acid and in some case catalyze the subsequent oxidation to 10-ketostearic acid (Heo and Kim 2009 Kuo et al. 2000, 2002 Kuo and Levinson 2006). The reaction shows moderate stereospecificity (Gocho et al. 1995). Two groups cloned independently the hydratases from the Pseudomonas strain 3266 (Bevers et al. 2009) and Streptococcus pyogenes... 

Kuo TM, Levinson WE (2006) Biocatalytic production of 10-hydroxystearic acid, 10-ketosteaiic acid, and their primary fatty amides. Agriculture 83(8) 671-675 Kuo TM, Lanser AC, Nakamura LK, Hou CT (2000) Production of 10-ketostearic acid and 10-hydroxystearic acid by strains of Sphingobacterium thalpophilum isolated fi om composted manure. Curr Microbiol 40 105-109. doi 10.1007/s002849910020... 

Lactarinic acid. 6-Oxostearic acid. 6-Ketostearic acid... 

Table 6. In a similar way 2-trans-7,10-20 3 CoA, 2-trans-9,12-20 3 CoA and 2-trans-10,13-20 3 CoA were reduced at about the same rate as found for 2-trans-18 l CoA and 2-trans-8,ll-20 3 CoA -i e Table 6 The B-hydroxyacyl-CoA dehydrase and 2-trans-enoyl-CoA reductase reactions are thus not highly substrate specific. Since both of these reactions proceed much more readily than the condensation reaction it might suggest that two or more independent condensing enzymes contribute there products to a common set of enzymes for subsequent reactions. Failure of dietary modification to alter the rates of these two reactions supports this hypothesis. Moreover, we have also shown that the CoA derivative of 3-keto-stearic acid was converted to stearic acid at least four times as rapidly as B-ketostearic acid was produced from 16 0 CoA and malonyl-CoA., The B-keto reductase reaction would thus not be rate limiting in this metabolic process. It thus appears that the rate at which an acid is chain elongated is dictated by the rate of the condensation reaction and that the rate of this reaction is controlled by structural features which are an inherent part of the substrate.

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