Studies on N-Acetyl-β-D-glucosaminidase of Aspergillus oryzae

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Abstract
It was found that several sugars accepted the N-acetylglucosaminyl residue in the transglycosylation reaction catalyzed by N-acetyl-β-D-glucosaminidase (EC 3. 2. 1. 30). To examine the acceptor site in the enzyme protein, the efficiencies of the various acceptors were examined. It was found that their efficiencies decreased in the following order; N-acetylglucosamine>N-formylglucosamine>glucose (galactose)>2-deoxyglucose>mannose. Among the alcohols tested as acceptors, the order was: primary alcohols>the corresponding secondary alcohols (tertiary alcohols had no acceptor ability); 1-pentanol>1-butanol>1-propanol>ethanol>methanol, glycerol> ethylene glycol>erythritol>xylitol>glucitol>N-acetylglucosaminitol. These results suggested that the structure of the acceptor hexose at carbon 2 is important in the interaction of the acceptor and the acceptor site of the enzyme, that an alkyl chain easily enters the acceptor site and that the acceptor ability of polyalcohols decreases with increase in chain length. The three step mechanism shown in the following equation was postulated for the transglycosylation reaction: The ratio ki/kh, defined as the transfer ratio (Ri), was determined for several alcohols.

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