원문정보
초록
영어
Xylanase (EC 3.2.1.8) is the name given to a class of enzymes which degrade the linear polysaccharide beta-1,4-xylan into xylose, thus breaking down hemicellulose, which is a major component of the cell wall of plants. Previously, a new xylanase gene, KRICT-PX1 isolated from
Paenibacillus sp. HPL-001 was expressed in E. coli, and the biochemical properties of the enzyme was examined. Error-Prone PCR conducted on the xylanase gene KRICT-PX1, and produced a mutation library. Enhanced xylanase activity from mutant clones were effectively identified using DNS assay in 96-well micro-plate after sonic cell disruption. Among 272 mutant clones, a P1H1 clone showing the strongest xylanase activity was selected. The xylanase activity of the P1H1 xylanase was 53.5 U/mg protein at pH 7 and 50°C, which is approximately 5 time-increased comparing to the original KRICT-PX1 xylanase with the activity of 10.25 U/mg protein at the same condition. The TLC analysis of the products catalyzed by two xylanases revealed that the hydrolysis of birchwood xylan by P1H1 xylanase was significantly greater than that of KRICT-PX1. DNA sequencing of the P1H1 clone showed that it had one amino acid substitution (168Gly￫Gln). Further research on the biochemical property and the structural analysis of this point-mutated xylanase will be necessary for the study of catalysis mechanism of xylanase.