Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 17, 2005
Publication Date: March 17, 2005
Citation: Li, X., Jordan, D.B., Cotta, M.A. 2005. Substrate specificities of two glycoside hydrolase family 11 xylanases [abstract]. American Chemical Society. Paper No. 066. Technical Abstract: Xylanase A (XynA) of the polycentric anaerobic fungus Orpinomyces PC-2 is composed of a catalytic module and a noncatalytic docking module connected by a linker sequence. The catalytic module spanning amino acid residues 29 to 255 of XynA with a mass of 25214 Da has been produced by Escherichia coli and purified by column chromatography. The mature xylanase II (XynII) of Trichoderma reesei is composed of a single catalytic module with a mass of 20 kDa. Both XynA and XynII catalytic modules belong to glycoside hydrolase family 11. Neither XynA nor XynII hydrolyzed xylan purified from corn fiber but in the presence of an alpha-L-arabinofuranosidase, they exhibit high levels of activity toward corn fiber xylan. XynA and XynII have comparible levels of activities (kcat between 645-2080 s**-1) toward oat spelt xylan, corn cob xylan, and wheat soluble xylan. A drastic difference between XynA and XynII is that XynA is highly active against wheat insoluble xylan with a kcat of 2150 s**-1 while XynII is virtually inactive (kcat<20.0 s**-1) towards this xylan. Mutational and structural analyses are underway to understand why the two enzymes behave so differently on wheat insoluble xylan.