Publications

• Trehalase: stereocomplementary hydrolytic and glucosyl transfer reactions with alpha- and beta-D-glucosyl fluoride.

  Hehre E.J., Sawai T., Brewer C.F., Nakano M., Kanda T.

  A new understanding has been obtained of the catalytic capabilities of trehalase, an enzyme heretofore held to be strictly specific for hydrolyzing alpha, alpha-trehalose and devoid of transglycosylative ability. Highly purified rabbit renal cortical trehalase and a partly purified Candida tropica ... >> More

  A new understanding has been obtained of the catalytic capabilities of trehalase, an enzyme heretofore held to be strictly specific for hydrolyzing alpha, alpha-trehalose and devoid of transglycosylative ability. Highly purified rabbit renal cortical trehalase and a partly purified Candida tropicalis yeast trehalase were found to utilize both alpha- and beta-D-glucosyl fluoride as substrates. In each case, the reactions were competitively inhibited by alpha, alpha-trehalose. Both enzymes catalyzed rapid hydrolysis of alpha-D-glucosyl fluoride to form beta-D-glucose (also, of alpha, alpha-trehalose to form equimolar alpha- and beta-D-glucose). In addition, digests of beta-D-glucosyl fluoride plus alpha-D-[14C]-glucopyranose with either trehalase (but not controls of enzyme with alpha-D-[14C]glucopyranose alone) yielded small amounts of radioactive trehalose (alpha-D-glucopyranosyl alpha-D-[14C]glucopyranoside) which does not accumulate since it is rapidly hydrolyzed. Trehalase thus catalyzes two stereocomplementary types of glycosylation reactions: (I) alpha-D-glucosyl fluoride (or alpha, alpha-trehalose) + H2O leads to beta-D-glucose + HF (or alpha-D-glucose); (II) beta-D-glucosyl fluoride + alpha-D-glucopyranose leads to alpha, alpha-trehalose + HF. Such behavior shows that the catalytic groups of trehalase, as recently found for other glycosylases, are functionally flexible. The results illustrate the inadequacy of conventional views of carbohydrase specificity and the rigor, as a basic guiding principle, of the concept that glycoside hydrolases and glycosyltransferases form a class of glycosylases effecting glycosyl/proton interchange. << Less

  Biochemistry 21:3090-3097(1982) [PubMed] [EuropePMC]

• Catalytic reaction mechanism based on alpha-secondary deuterium isotope effects in hydrolysis of trehalose by European honeybee trehalase.

  Mori H., Lee J.H., Okuyama M., Nishimoto M., Ohguchi M., Kim D., Kimura A., Chiba S.

  Trehalase, an anomer-inverting glycosidase, hydrolyzes only alpha,alpha-trehalose in natural substrates to release equimolecular beta-glucose and alpha-glucose. Since the hydrolytic reaction is reversible, alpha,alpha-[1,1'-(2)H]trehalose is capable of synthesis from [1-(2)H]glucose through the re ... >> More

  Trehalase, an anomer-inverting glycosidase, hydrolyzes only alpha,alpha-trehalose in natural substrates to release equimolecular beta-glucose and alpha-glucose. Since the hydrolytic reaction is reversible, alpha,alpha-[1,1'-(2)H]trehalose is capable of synthesis from [1-(2)H]glucose through the reverse reaction of trehalase. alpha-Secondary deuterium kinetic isotope effects (alpha-SDKIEs) for the hydrolysis of synthesized alpha,alpha-[1,1'-(2)H]trehalose by honeybee trehalase were measured to examine the catalytic reaction mechanism. Relatively high k(H)/k(D) value of 1.53 for alpha-SDKIEs was observed. The data imply that the catalytic reaction of the trehalase occurs by the oxocarbenium ion intermediate mechanism. In addition, the hydrolytic reaction of glycosidase is discussed from the viewpoint of chemical reactivity for the hydrolysis of acetal in organic chemistry. As to the hydrolytic reaction mechanism of glycosidases, oxocarbenium ion intermediate and nucleophilic displacement mechanisms have been widely recognized, but it is pointed out for the first time that the former mechanism is rational and valid and generally the latter mechanism is unlikely to occur in the hydrolytic reaction of glycosidases. << Less

  Biosci Biotechnol Biochem 73:2466-2473(2009) [PubMed] [EuropePMC]