Catalytic thiol and carboxylate: role of cysteine and glutamic acid in the xylosidic activity of endoxylanase from Chainia sp. (NCL 82-5-1).
Chemical modification of the endoxylanase from Chainia sp. with group-specific chemical modifiers in the absence and presence of substrate and kinetics of modification revealed the involvement of a thiol and a carboxylate in the catalytic function of the enzyme. The active-site peptides were chemically labeled and sequenced. The sequence alignment of the chemically labeled peptide with other family G/11 xylanases showed that the catalytic glutamate of Chainia xylanase is located in a highly homologous region and may function as an acid/base catalyst while thiol of the Cys may function as a nucleophile.
Subray
S H
SH
Division of Biochemical Sciences, National Chemical Laboratory, Pune, 411 008, India.
Ameeta
R K
RK
Krishna
N G
NG
Khan
I M
IM
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000302:isolation & purification; D001665:Binding Sites; D002264:Carboxylic Acids / Q000378:metabolism*; D002384:Catalysis; D003545:Cysteine / Q000378:metabolism* / Q000502:physiology; D043364:Endo-1,4-beta Xylanases; D004789:Enzyme Activation; D018698:Glutamic Acid / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D010455:Peptides / Q000302:isolation & purification / Q000378:metabolism; D013306:Streptomycetaceae / Q000201:enzymology; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*; D014995:Xylosidases / Q000378:metabolism*
D000596:Amino Acids; D002264:Carboxylic Acids; D010455:Peptides; D013438:Sulfhydryl Compounds; D018698:Glutamic Acid; D014994:Xylose; D014995:Xylosidases; D043364:Endo-1,4-beta Xylanases; D003545:Cysteine