CHEMICAL MODIFICATION OF XYLANASE FROM CHAINIA SP (NCL 82.5.1)

The high molecular weight xylanase from Chainia (NCL 82.5.1) is extrac ellular, cellulase-free and stable at alkaline pH (pH 8.0) at 50 degre es C. The enzyme showed inhibition by N-bromosuccinimide(NBS) and by c ysteine-specific reagents p-hydroxy mercuric-benzoate(PHMB) and N-ethy l maleimide(NEM) implying that tryptophan and cysteine are present at or near the active site of. the enzyme. The enzyme was reversibly inhi bited by low concentrations (0.5 M) of guanidine hydrochloride (Gdn.HC l) indicative of the presence of a carboxylate group in the active sit e of the enzyme. Kinetics of inactivation of enzyme by Gdn.HCl reveale d that the essential carboxylate residues are present at the substrate -binding region of the enzyme.