| 摘要 |
PCT No. PCT/DE93/00198 Sec. 371 Date Aug. 11, 1994 Sec. 102(e) Date Aug. 11, 1994 PCT Filed Mar. 5, 1993 PCT Pub. No. WO93/18138 PCT Pub. Date Sep. 16, 1993.A keto ester reductase capable of being used in an NADH-dependent enzymatic reaction for converting beta , gamma and delta ketonic acid esters into the corresponding optically active beta , gamma and delta hydroxycarboxylic acid esters can be isolated from strains of Candida parapsilosis, Yarrowinia cellobiosa, Rhodococcus erythropolis or Pseudomonas acidovorans, preferably cultivated on a long -chain alkane and/or alkane acid-containing culture medium, approximately in the presence of an inductor. The microorganism is preferrably, Candida parapsilosis DSM 70125. A usable enzyme preparation can be recovered by fractionated PEG-precipitation from the cell raw extract: high specific activities (for example 1855 U/mg) may then be obtained by chromatographic purification. The keto ester reductase is characterized as having a molecular weight of 136 kDa+11 kDa as determined by gel permeation chromatography on Sephadex G-200, a pH optimum for conversion of the keto ester to the hydroxy acid esters between pH 7.8 and 8.0 and for the reverse reaction of converting the acid esters to the keto esters at a pH optimum of 9.5, and a temperature optimum between 36 DEG and 40 DEG C. for conversion of the keto esters to the hydroxy acid esters and from 50 DEG to 56 DEG C. for the reverse reaction of converting the acid esters to the keto esters. Not only (possibly substituted) so-called ketonic esters are accepted, but also number of other oxo-compounds among which diketones, (possibly substituted, in particular halogenated) aliphatic alicyclic and aromatic ketones, as well as ketoacetals and aldehydes. The S-enantiomer-forming reduction is supplemented by the possibility to recover R-enantiomers from racemates by oxidizing the S-enantiomer and separating the oxo-compound.
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