title: Isolation and biochemical characterization of two novel metagenome-derived esterases.
abstract: Environmental DNA from soil and water samples was extracted to construct a plasmid library and a fosmid library containing 19,500 and 20,400 clones, respectively. Two esterases (EstP2K and EstF4K) were finally isolated from each library based on activity screening, and both of them were characterized in this study. The esterase EstF4K consists of 396 amino acids with an SMTK motif which belongs to family VIII esterase/lipase. The amino acid sequence of EstF4K showed 83 % identity with that of EstA3, a reported esterase isolated from uncultured organisms of soil. EstP2K is composed of 224 amino acids in size and shows only 37 % identity with a putative lipase of Neisseria elongata subsp. The purified EstF4K was optimally active at pH 8.0 and 50 °C. It was remarkably active and very stable in the presence of 30 % dimethyl sulfoxide. Activity fingerprint of EstF4K displayed a higher level of activity toward short-chain fatty acid p-nitrophenyl (pNP) esters, while EstP2K preferred bias for pNP caprylate ester. The optimum reaction temperature and pH for EstP2K are 45 °C and 7.5, respectively, and the enzyme exhibited strong tolerance in the presence of 30 % methanol. EstF4K and EstP2K showed opposite enantioselectivity for methyl 3-phenylglycidate, a chiral synthon for the synthesis of Taxol® side chain.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, People's Republic of China. ouyanglm@ecust.edu.cn
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Ouyang
authors.forename: Jia-Ying
authors.initials: JY
authors.lastname: Liu
authors.forename: Ming
authors.initials: M
authors.lastname: Qiao
authors.forename: Jian-He
authors.initials: JH
authors.lastname: Xu
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D003001:Cloning, Molecular; D004795:Enzyme Stability; D004950:Esterases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D005618:Fresh Water / Q000737:chemistry; D015723:Gene Library; D006863:Hydrogen-Ion Concentration; D054892:Metagenome; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D012987:Soil / Q000737:chemistry; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D012987:Soil; D004950:Esterases