Characteristics and function of Alcaligenes sp. NBRC 14130 esterase catalysing the stereo-selective hydrolysis of ethyl chrysanthemate.

AIMS: Alcaligenes sp. NBRC 14130 was found as a strain hydrolysing a mixture of (+/-)-trans- and (+/-)-cis ethyl chrysanthemates to (1R,3R)-(+)-trans-chrysanthemic acid. The Alcaligenes cells also have hydrolytic activity for 6-aminohexanoate-cyclic dimer (6-AHCD, 1,8-diazacyclotetradecane-2,9-dione). The correlation of function on the enzyme from the Alcaligenes strain with hydrolysis activities for both ethyl chrysanthemate and 6-AHCD was demonstrated. METHODS AND RESULTS: The esterase was purified to homogeneity. The purified esterase hydrolysed 20 mmol l(-1) ester including the four stereoisomers to the corresponding (+)-trans acid with a 37% molar conversion of ethyl (+)-trans chrysanthemate. The esterase showed high hydrolytic activity for various short-chain fatty acid esters, n-hexane amide and 6-AHCD. The amino acid sequence of the Alcaligenes esterase was identical to that of Arthrobacter 6-AHCD hydrolase (EC 3.5.2.12) and similar to that of fatty acid amide hydrolase (EC 3.5.1.4) from Rattus norvegicus, having both serine and lysine residues of the catalytic site and the consensus motif Gly-X-Ser-X-Gly. CONCLUSION: The stereo-selective hydrolytic activity was found in Alcaligenes sp. NBRC14130 by screening of ethyl chrysanthemate-hydrolysing activity in micro-organisms, and the purified esterase also acted on fatty acid esters and amides. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has demonstrated that there are great differences in the enzymatic properties, amino acid sequence and catalytic motif of esterases in both Alcaligenes and Arthrobacter globiformis with excellent stereo-selectivity for (+)-trans-ethyl chrysanthemate, but the amino acid sequence of Alcaligenes esterase is identical to that of Arthrobacter 6-AHCD hydrolase.

Microbial asymmetric oxidation of 2-butyl-1,3-propanediol.

Microbial asymmetric oxidation of 2-butyl-1,3-propanediol was investigated for an efficient synthesis of S- and R-enantiomers of 2-hydroxymethylhexanoic acid (2-HMHA). From an intensive survey of the stocked bacterial strains, Acetobacter pasteurianus IAM 12073 and Pseudomonas putida IFO 3738 were found to show the highest S- and R-2-HMHA-producing activity, respectively. Under optimized conditions, A. pasteurianus (351 mg dry cell weight) and P. putida (642 mg dry cell weight) cells produced 12.0 g l(-1) S-2-HMHA with 89% enantiomeric excess (e.e.) at 24 h of incubation and 5.1 g l(-1) R-2-HMHA with 94% e.e. at 35 h of incubation from 2-butyl-1,3-propanediol.

Synthesis of bis- and oligo-gem-difluorocyclopropanes using the olefin metathesis reaction

Synthesis of six types of novel bis- and oligo-gem-difluorocyclopropanes has been accomplished through the olefin metathesis reaction protocol. Two types of ruthenium-based olefin metathesis catalysts were tested: the ruthenium catalyst coordinated with 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene and tricyclohexylphosphine ligands gave better results than the ruthenium catalyst that coordinated with two tricyclohexylphosphine ligands.