Reference

Stereoselective reduction of b-keto esters by Geotrichum candidum

Stereoselective reduction of b-keto esters by Geotrichum candidum. Patel, Ramesh N.; McNamee, Clyde G.; Banerjee, Amit; Howell, Jeffrey M.; Robison, Robert S.; Szarka, Laszlo J. (Microb. Technol. Dep., Bristol-Myers Squibb Pharm. Res. Inst., New Brunswick, NJ 08903, USA). Enzyme Microb. Technol., 14(9), 731-8 (English) 1992. CODEN: EMTED2. ISSN: 0141-0229. DOCUMENT TYPE: Journal CA Section: 16 (Fermentation and Bioindustrial Chemistry) A key chiral intermediate, S(-)-4-chloro-3-hydroxybutanoic acid Me ester (I) was made in high optical purity by the stereoselective redn. of 4-chloro-3-oxobutanoic acid Me ester (II) by cell suspensions of G. candidum SC 5469. A reaction yield of 95% and optical purity of 96% was obtained for I by glucose-, acetate-, or glycerol-grown cells (10%) of G. candidum SC 5469. Substrate was used at 10 mg/mL. The optical purity of I was increased to 99% by heat treatment of cell suspensions (55° for 30 min) prior to incubation at 28°. Glucose-grown cells of G. candidum SC 5469 also catalyzed the stereoselective redn. of the Et, iso-Pr, and tert-Bu esters of 4-chloro-3-oxobutanoic acid and the Me and Et esters of 4-bromo-3-oxobutanoic acid. A reaction yield of >85% and optical purity of >94% were obtained. The NADP-dependent oxidoreductase responsible for the stereoselective redn. of the b-keto esters of 4-chloro- and 4-bromo-3-oxobutanoic acid was purified 100-fold. The mol. wt. of the purified enzyme is 950,000. The purified oxidoreductase was immobilized on Eupergit C and used to catalyze the redn. of II to I.Several substances like 86728-85-0 may be metioned in this study. The cofactor NADP required for the redn. reaction was regenerated by glucose dehydrogenase. .

Stereochemical control of yeast reductions

Stereochemical control of yeast reductions. 5. Characterization of the oxidoreductases involved in the reduction of b-keto esters. Shieh, Woanru; Gopalan, Aravamudan S.; Sih, Charles J. (Sch. Pharm., Univ.Some chemicals with cas registry numbers like 86728-85-0 are also used. Wisconsin, Madison, WI 53706, USA). J. Am. Chem. Soc., 107(10), 2993-4 (English) 1985. CODEN: JACSAT. 86728-85-0 which is the cas registry number of some chemical is mentioned. ISSN: 0002-7863. DOCUMENT TYPE: Journal CA Section: 7 (Enzymes) Three b-keto reductases, purified to homogeneity from the cytosolic fraction of bakers' yeast, were capable of actively reducing 4-chloroacetoacetic esters to yield corresponding carbinolic products of high optical purity [>0.97 enantiomeric excess (ee)]. All of them utilized NADPH preferentially as the coenzyme. One of these enzymes (mol. wt. = 2,400,000) possessed phys. and chem. properties reminiscent of fatty acid synthetase and reduced b-keto esters to yield carbinols of D-configuration. Although the natural substrates for the other 2 enzymes have not yet been defined, they were readily resolved on a hydroxylapatite column. The faster moving protein (D-enzyme) had a mol. wt. of 38,000 and reduced b-keto esters to yield D-carbinolic products, whereas L-enzyme (mol. wt. = 74,000) afforded L-carbinols. Because mammalian L-3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) in the presence of NADH reduced 4-chloroacetoacetic esters to (R)-4-chloro-3-hydroxybutanoates of high ee (>0.97), this reductase activity was carefully searched for in bakers' yeast. Whereas mitochondrial fractions of bakers' yeast actively reduced acetoacetyl-CoA, only a trace of this reductase activity was detectable. This observation indicated that L-3-hydroxyacyl-CoA dehydrogenases of different species have marked differences in substrate specificities. To gain an insight into the influence of the ester substituent on the enantioselective redn. of g-chloro-b-keto esters by intact bakers' yeast, the kcat (turnover no.) and Km for the 3 enzymes on various 4-chloroacetoacetic esters were measured. ..