Degradation of rice bran hemicellulose by Paenibacillus sp. strain HC1: gene cloning, characterization and function of beta-D-glucosidase as an enzyme involved in degradation.
A bacterium (strain HC1) capable of assimilating rice bran hemicellulose was isolated from a soil and identified as belonging to the genus Paenibacillus through taxonomical and 16S rDNA sequence analysis. Strain HC1 cells grown on rice bran hemicellulose as a sole carbon source inducibly produced extracellular xylanase and intracellular glycosidases such as beta-D-glucosidase and beta-D-arabinosidase. One of them, beta-D-glucosidase, was further analyzed. A genomic DNA library of the bacterium was constructed in Escherichia coli and gene coding for beta-D-glucosidase was cloned by screening for beta-D-glucoside-degrading phenotype in E. coli cells. Nucleotide sequence determination indicated that the gene for the enzyme contained an open reading frame consisting of 1,347 bp coding for a polypeptide with a molecular mass of 51.4 kDa. The polypeptide exhibits significant homology with other bacterial beta-D-glucosidases and belongs to glycoside hydrolase family 1. Beta-D-Glucosidase purified from E. coli cells was a monomeric enzyme with a molecular mass of 50 kDa most active at around pH 7.0 and 37 degrees C. Strain HC1 glycosidases responsible for degradation of rice bran hemicellulose are expected to be useful for structurally determining and molecularly modifying rice bran hemicellulose and its derivatives.
Harada
Karen Mine
KM
Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
Tanaka
Keiko
K
Fukuda
Yasuki
Y
Hashimoto
Wataru
W
Murata
Kousaku
K
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D016937:Gram-Positive Endospore-Forming Rods / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000378:metabolism*; D001617:beta-Glucosidase / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification
D011134:Polysaccharides; C007916:hemicellulose; D001617:beta-Glucosidase