title: Characterization of a glycoside hydrolase family 1 β-galactosidase from hot spring metagenome with transglycosylation activity.
abstract: A novel, thermostable, alkalophilic β-D-galactosidase (Mbgl) was isolated from a metagenome of geothermal springs in northern Himalayan region of India. Mbgl was 447 amino acids in size and had conserved catalytic residues E170 and E358, indicating that it belonged to family 1 of glycosyl hydrolases showing maximum homology (89 %) with uncharacterized β-galactosidase of Eubacterium, Meiothermus ruber DSM1279. Temperature and pH optima of Mbgl were 65 °C and 8.0 respectively, and it retained 80 % activity even at pH 10.0. Mbgl was active as a homotetramer, recognized β-(1,4)-D-galactoside as the preferred glycosidic bond, and preferentially hydrolyzed pNPgal with K(m) 3.33 mM and k(cat) 2,000 s(-1). It displayed high transglycosylation activity with wide acceptor specificity including hexoses and pentoses leading to the formation of prebiotic galacto-oligosaccharides whereas its lactose hydrolysis potential was low.
authors.affiliation: Department of Biotechnology, Panjab University, Chandigarh 160014, India.
authors.forename: Richa
authors.initials: R
authors.lastname: Gupta
authors.forename: Tanvi
authors.initials: T
authors.lastname: Govil
authors.forename: Neena
authors.initials: N
authors.lastname: Capalash
authors.forename: Prince
authors.initials: P
authors.lastname: Sharma
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; D004795:Enzyme Stability; D045482:Hot Springs / Q000382:microbiology*; D007700:Kinetics; D054892:Metagenome; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D001616:beta-Galactosidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001616:beta-Galactosidase