earticle

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. From 272 mutant clones, a P1H1 clone showing strong xylanase activity was selected. The xylanase activity of the P1H1 was 53.5 U/mg protein at pH7 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 of birchwood xylan catalyzed by two xylanases revealed that the hydrolysis by P1H1 xylanase was significantly faster 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 the point-mutated xylanase will be necessary for the catalysis mechanism of xylanase.