title: A novel esterase from a marine metagenomic library exhibiting salt tolerance ability.
abstract: A putative lipolytic enzyme gene, named as est9x, was obtained from a marine microbial metagenome of the South China Sea. Sequence analysis showed that Est9X shares lower than 27% sequence identities with the characterized lipolytic enzymes, but possesses a catalytic triad highly conserved in lipolytic enzymes of the α/β hydrolase superfamily. By phylogenetic tree construction, Est9X was grouped into a new lipase/esterase family. To understand Est9X protein in depth, it was recombinantly expressed, purified, and biochemically characterized. Within potential hydrolytic activities, only lipase/esterase activity was detected for Est9X, confirming its identity as a lipolytic enzyme. When using p-nitrophenol esters with varying lengths of fatty acid as substrates, Est9X exhibited the highest activity to the C2 substrate, indicating it is an esterase. The optimal activity of Est9X occurred at a temperature of 65°C, and Est9X was pretty stable below the optimum temperature. Distinguished from other salttolerant esterases, Est9X's activity was tolerant to and even promoted by as high as 4 M NaCl. Our results imply that Est9X is a unique esterase and could be a potential candidate for industrial application under extreme conditions.
authors.affiliation: School of Life Sciences, Anhui University, Hefei, Anhui 230601, China, Anhui Provincial Engineering Technology Research Center of Microorganisms and Biocatalysis, Hefei, Anhui 230601, China.
authors.forename: Zemin
authors.initials: Z
authors.lastname: Fang
authors.forename: Jingjing
authors.initials: J
authors.lastname: Li
authors.forename: Quan
authors.initials: Q
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Fang
authors.forename: Hui
authors.initials: H
authors.lastname: Peng
authors.forename: Xuecheng
authors.initials: X
authors.lastname: Zhang
authors.forename: Yazhong
authors.initials: Y
authors.lastname: Xiao
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002681:China; D004950:Esterases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015723:Gene Library; D056186:Metagenomics; D008969:Molecular Sequence Data; D010802:Phylogeny; D055049:Salt Tolerance; D012623:Seawater / Q000382:microbiology*; D016415:Sequence Alignment; D012965:Sodium Chloride / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D012965:Sodium Chloride; D004950:Esterases