Identification of the catalytic nucleophile in the cellulase from Schizophyllum commune and assignment of the enzyme to Family 5, subtype 5 of the glycosidases.
Differential chemical modification of the cellulase from Schizophyllum commune with [N-methyl-3H]1-ethyl-3(4-azonia-4,4-dimethylpentyl)-carbodiimide in the presence and absence of substrate identified an active site glutamate residue within the peptide: Leu-Gln-Ala-Ala-Thr-Glu-Trp-Leu-(Lys). This Glu residue is proposed to participate in binding of substrate as amino acid sequence homology studies combined with mechanism-based inhibition of the cellulase with 4',5'-epoxypentyl-beta-D-cellobioside identified a neighboring Glu residue, which conforms to the Glu-X-Gly motif of Family 5 glycosidases, as the catalytic nucleophile. These data allow the assignment of the S. commune cellulase to Family 5, subtype 5 of the glycosidases.
Clarke
A J
AJ
Department of Microbiology, University of Guelph, Ont., Canada. AClarke@Micro.UoGuelph.CA
Drummelsmith
J
J
Yaguchi
M
M
D000595:Amino Acid Sequence; D001665:Binding Sites; D002234:Carbodiimides; D002480:Cellulase / Q000737:chemistry* / Q000145:classification* / Q000378:metabolism; D018698:Glutamic Acid; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000145:classification*; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D012567:Schizophyllum / Q000201:enzymology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D002234:Carbodiimides; D010446:Peptide Fragments; D018698:Glutamic Acid; C044568:1-ethyl-3-(4-azonia-4,4-dimethylpentyl)carbodiimide; D006026:Glycoside Hydrolases; D002480:Cellulase