TY - JOUR
T1 - Scope and mechanism of carbohydrase action. Stereocomplementary hydrolytic and glucosyl-transferring actions of glucoamylase and glucodextranase with alpha- and beta-D-glucosyl fluoride.
AU - Kitahata, S.
AU - Brewer, C. F.
AU - Genghof, D. S.
AU - Sawai, T.
AU - Hehre, E. J.
N1 - Copyright:
Medline is the source for the citation and abstract of this record.
PY - 1981/6/25
Y1 - 1981/6/25
N2 - Rhizopus niveus glucoamylase and Arthrobacter globiformis glucodextranase, which catalyze the hydrolysis of starch and dextrans, respectively, to form D-glucose of inverted (beta) configuration, were found to convert both alpha- and beta-D-glucosyl fluoride to beta-D-glucose and hydrogen fluoride. Each enzyme directly hydrolyzes alpha-D-glucosyl fluoride but utilizes th beta-anomer in reactions that require 2 molecules of substrate and yield glucosyl transfer products which are then rapidly hydrolyzed to form beta-D-glucose. Various D-glucopyranosyl compounds serve as acceptors for such reactions. Mixtures of beta-D-glucosyl fluoride and methyl-alpha-D-glucopyranoside[14C], incubated with either enzyme, yielded both methyl-alpha-D-glucopyranosyl-(1 leads to 4)-alpha-D-[14C]glucopyranoside and methyl-alpha-D-glucopyranosyl-(1 leads to 6)-alpha-D-[14C]glucopyranoside. Glucoamylase produced more of the alpha-maltoside; glucodextranase produced more of the alpha-isomaltoside. Thus, both "exo-alpha-glucan hydrolases" emerge as glucosylases that catalyze stereospecifically complementary hydrolytic and transglucosylative reactions with glucosyl donors of opposite configuration. These reactions not only provide a new view of the catalytic capabilities of these supposedly strict hydrolases; they also furnish a basis for defining a detailed mechanism for catalysis. Present results, together with those of several recent studies from this laboratory (especially similar findings obtained with beta-amylase acting on alpha- and beta-maltosyl fluoride (Hehre, E. J., Brewer, C. F., and Genghof, D. S. (1979) J. Biol. Chem. 254, 5942-5950), provide strong new evidence for the functional flexibility of the catalytic groups of carbohydrases.
AB - Rhizopus niveus glucoamylase and Arthrobacter globiformis glucodextranase, which catalyze the hydrolysis of starch and dextrans, respectively, to form D-glucose of inverted (beta) configuration, were found to convert both alpha- and beta-D-glucosyl fluoride to beta-D-glucose and hydrogen fluoride. Each enzyme directly hydrolyzes alpha-D-glucosyl fluoride but utilizes th beta-anomer in reactions that require 2 molecules of substrate and yield glucosyl transfer products which are then rapidly hydrolyzed to form beta-D-glucose. Various D-glucopyranosyl compounds serve as acceptors for such reactions. Mixtures of beta-D-glucosyl fluoride and methyl-alpha-D-glucopyranoside[14C], incubated with either enzyme, yielded both methyl-alpha-D-glucopyranosyl-(1 leads to 4)-alpha-D-[14C]glucopyranoside and methyl-alpha-D-glucopyranosyl-(1 leads to 6)-alpha-D-[14C]glucopyranoside. Glucoamylase produced more of the alpha-maltoside; glucodextranase produced more of the alpha-isomaltoside. Thus, both "exo-alpha-glucan hydrolases" emerge as glucosylases that catalyze stereospecifically complementary hydrolytic and transglucosylative reactions with glucosyl donors of opposite configuration. These reactions not only provide a new view of the catalytic capabilities of these supposedly strict hydrolases; they also furnish a basis for defining a detailed mechanism for catalysis. Present results, together with those of several recent studies from this laboratory (especially similar findings obtained with beta-amylase acting on alpha- and beta-maltosyl fluoride (Hehre, E. J., Brewer, C. F., and Genghof, D. S. (1979) J. Biol. Chem. 254, 5942-5950), provide strong new evidence for the functional flexibility of the catalytic groups of carbohydrases.
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M3 - Article
C2 - 6787047
AN - SCOPUS:0019888206
SN - 0021-9258
VL - 256
SP - 6017
EP - 6026
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 12
ER -