Glucosidase cleaves

An a-glucosidase cleaves glucose residues from the nonreducing ends of oligosaccharides and also cleaves the a-1,4 bond of maltose, releasing the two glucose residues. 

Glucosidase cleaved alangiside to yield D-glucose and the aglucone 27. The mass spectrum of alangiside showed a weak M+ ion at m/e 505 and a medium peak at m/e 343. The base peak in the spectrum appeared at m/e 21 A, and there were characteristic fragments of isoquinoline ions at m/e 178... 

Hydrolases. Enzymes catalysing the hydrolytic cleavage ofC —O, C —N and C —C bonds. The systematic name always includes hydrolase but the recommended name is often formed by the addition of ase to the substrate. Examples are esterases, glucosidases, peptidases, proteinases, phospholipases. Other bonds may be cleaved besides those cited, e.g. during the action of sulphatases and phosphatases. 

An example of a direct spectrophotometrical assay is the use of synthetic peptide -nitroanilide substrates to determine protease activity. The /)-nitroani1ine group Hberated from the substrates by the protease can be determined spectrophotometricaHy at 410 nm. An example of an indirect (coupled) spectrophotometric assay is the determination of a-amylase using -nitrophenyLmaltoheptaoside. Initially, the substrate is cleaved by the a-amylase and subsequentiy one of the reaction products, -nitrophenyLmaltotrioside, is cleaved by a-glucosidase, hberating -nitrophenyl, a chromophore... 

Endogenous and exogenous enzymes — While the role of (3-glucosidase affecting betalains is quite clear, the roles of polyphenoloxidase and peroxidase are less obvious. Betacyanin glycosides may be cleaved into the corresponding aglycones, the... 

Endo-2-acetamido-2-deoxy-)3-D-glucosidase has been used in structural studies of glycopeptides.30 The enzyme cleaves the linkage between the two 2-amino-2-deoxyglucose residues that constitute the chitobiose residue linked to L-asparagine in glycoproteins containing... 

Although dilute aqueous acid hydrolyzed the methyl and benzyl a-D-fructofuranosides approximately 8 and 16 times as rapidly as sucrose, their method of preparation showed them to be unaffected by any of the enzymes active in a fermenting yeast suspension. Purified yeast invertase, proven free of a-D-glucosidases (maltases), could therefore contain no enzyme capable of hydrolyzing the above two a-D-fructo-furanosides, but did contain constituents that readily cleaved the beta isomers and also sucrose. The latter is accordingly a /S-D-fructofuranos-ide. When the evidence is put in this way, the present uncertainties as to whether purified invertase preparations include one or a number of /3-D-fructofuranosidases, and whether or not sucrose, methyl and... 

Polyphenols with attached glucose are potential substrates for endogenous human enzymes, while attached rhamnose is not a substrate for human (3-glucosidases and so is only cleaved by colon microflora a-rhamnosidases [63]. 

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