title: Rice family GH1 glycoside hydrolases with beta-D-glucosidase and beta-D-mannosidase activities.
abstract: Plant beta-D-mannosidases and a rice beta-D-glucosidase, Os3BGlu7, with weak beta-D-mannosidase activity, cluster together in phylogenetic analysis. To investigate the relationship between substrate specificity and amino acid sequence similarity in family GH1 glycoside hydrolases, Os3BGlu8 and Os7BGlu26, putative rice beta-D-glucosidases from this cluster, and a beta-D-mannosidase from barley (rHvBII), were expressed in Escherichia coli and characterized. Os3BGlu8, the amino acid sequence and molecular model of which are most similar to Os3BGlu7, hydrolysed 4-nitrophenyl-beta-D-glucopyranoside (4NPGlc) faster than 4-nitrophenyl-beta-D-mannopyranoside (4NPMan), while Os7BGlu26, which is most similar to rHvBII by these criteria, hydrolysed 4NPMan faster than 4NPGlc. All the enzymes hydrolyzed cellooligosaccharides with increased hydrolytic rates as the degree of polymerization increased from 3-6, but only rHvBII hydrolyzed cellobiose with a higher k(cat)/K(m) value than cellotriose. This was primarily due to strong binding of glucosyl residues at the+2 subsite for the rice enzymes, and unfavorable interactions at this subsite with rHvBII.
authors.affiliation: School of Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Teerachai
authors.initials: T
authors.lastname: Kuntothom
authors.forename: Sukanya
authors.initials: S
authors.lastname: Luang
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Harvey
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Fincher
authors.forename: Rodjana
authors.initials: R
authors.lastname: Opassiri
authors.forename: Maria
authors.initials: M
authors.lastname: Hrmova
authors.forename: James R
authors.initials: JR
authors.lastname: Ketudat Cairns
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D003001:Cloning, Molecular; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism; D001467:Hordeum / Q000201:enzymology; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D012275:Oryza / Q000201:enzymology*; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D001617:beta-Glucosidase / Q000378:metabolism*; D044902:beta-Mannosidase / Q000378:metabolism*
chemical_list: D006027:Glycosides; D007527:Isoenzymes; D009844:Oligosaccharides; D006026:Glycoside Hydrolases; D001617:beta-Glucosidase; D044902:beta-Mannosidase