The configurations at the anomeric carbon of the reaction products of some digestive carbohydrases

Semenza, Giorgio; Curtius, Hans−Christoph; Raunhardt, O.; Hore, P.; Müller, M.

doi:10.1016/s0008-6215(00)80902-7

Cited by 31 publications

(9 citation statements)

References 23 publications

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“…Although carbodiimides react with COOH groups [15], the alignments lead one to infer that similar stereochemical relationships of catalytic groups to substrate exist in the different enzymes. It is assumed, therefore, that gaAn Glu 180, like the homologous aspartates of S-I, acts as a base in the catalysis and mechanisms have been proposed [ 16,171 which are consistent with the retention and inversion of the product configuration as found for isomaltase [18] and glucoamylase [19].…”

Section: Introductionmentioning

confidence: 75%

Regional distant sequence homology between amylases, α‐glucosidases and transglucanosylases

1988

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Amylases possess short, conserved regions near functional side chains. Sequence comparison extends this relationship to comprise a maltase and a cyclodextrin glucanotransferase. Similarity also exists with intestinal sucrase-isomaltase and fungal glucoamylase near identified essential carboxyl groups. Homology between COOH-terminal regions of glucoamylase and cyclodextrin glucanotranserase may indicate raw-starch binding areas. It is suggested that amylases, alpha-glucosidases, and transglucanosylases acting on 1,4- and 1,6-alpha-glucosidic linkages share key structural features in the active centres.

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Section: Introductionmentioning

confidence: 75%

Regional distant sequence homology between amylases, α‐glucosidases and transglucanosylases

1988

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“…We chose a system based on GC, where both products (modified galactoses and glucoses) and substrates, could be detected as their pertrimethylsilyl derivatives. A similar system has been used in the study of the stereochemistry at C1 of the released galactose [34].…”

Section: Resultsmentioning

confidence: 99%

Substrate specificity of small‐intestinal lactase

Rivera‐Sagredo

Cañada

Nieto

et al. 1992

European Journal of Biochemistry

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Lactase-phlorizin hydrolase is a disaccharidase present in the small intestine of mammals. This enzyme has two active sites, one being responsible for the hydrolysis of lactose. Lactase activity is thought to be selective towards glycosides with a hydrophilic aglycon. In this work, we report a systematic study on the importance of each hydroxyl group in the substrate molecule for lactase activity. For this purpose, all of the monodeoxy derivatives of methyl b-lactoside and other lactose analogues are studied as lactase substrates. With respect to the galactose moiety, it is shown here that HO-3' and HO-2' are necessary for hydrolysis of the substrates by lactase. Using these chemically modified substrates, it has been confirmed that lactase does not behave as a typical P-galactosidase, since it does not show an absolute selectivity with respect to substitution and stereochemistry at C4' in the galactose moiety of the substrate. However, the glucose moiety, in particular the HO-6, appears to be important for substrate hydrolysis, although none of the hydroxyl groups seemed to be essential. In order to differentiate both activities of the enzyme, a new assay for the phlorizin-hydrolase activity has also been developed.Small-intestinal disaccharidases in higher animals are located in the luminal membrane of intestinal mucose where they hydrolyze the disaccharides in the diet and the oligosaccharides that arise in the intestinal lumen after a-amiIolysis of starch [l, 21. Lactase is the small-intestinal disaccharidase that splits the major 8-glycoside of the diet, lactose, to give glucose and galactose (Scheme 1). The enzyme has been the subject of considerable investigation because of its involvement in the most frequent genetically based syndrome in man, known as adult-type alactasia or lactose intolerance in the adult resulting in a remarkable decrease in lactase activity in adulthood which affects more than 33% of adult humans [I, 3,4].A biological clock appears to exist, causing a marked decline of lactase after weaning, except for individuals whose ancestors are dependent on a substantial consumption of milk and milk-derived products.It has been known for some time that, in addition to lactase activity, the enzyme carries a P-glucosidase activity refered to as phlorizin hydrolase [5-81, which is in fact a glycosylceramidase [9]. The enzyme is therefore named lactasephlorizin hydrolase or the intestinal P-glycosidase complex. We have now carried out a systematic study of the substrate specificity with respect to the lactase site of the bglycosidase complex from sheep small intestine, using chemically modified methyl P-lactoside derivatives. Methyl P-lactoside rather than lactose, has been used as a reference compound in order to simplify the analysis of the reaction mixtures. These chcmically modified substrates have been frequently used in the study of enzyme mechanisms [13 -161 and have proved extremely useful in probing the combining sites for the elucidation of specific interactions between proteins and carb...

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“…5). This result is of special interest since (i) LPH, like the Agrobacterium enzyme, catalyzes the glycosidic bond cleavage with the retention of the configuration at C-1 of the product (49), and (ii) LPH domain II is removed from pro-LPH by proteolytic processing in vivo (29). Therefore, we predict that domain III Glu-1273 and Glu-1749 of human LPH are directly involved in catalysis and that LPH domain II is a noncatalytic polypeptide.…”

Section: E S L H -------Q W H H Y N S H H R P Q Qqgih V G I Vrln S D mentioning

confidence: 95%

Nucleotide sequences of the arb genes, which control beta-glucoside utilization in Erwinia chrysanthemi: comparison with the Escherichia coli bgl operon and evidence for a new beta-glycohydrolase family including enzymes from eubacteria, archeabacteria, and humans

et al. 1992

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The phytopathogenic bacterium Erwinia chrysanthemi, unlike other members of the family Enterobacteriaceae, is able to metabolize the ,B-glucosides, arbutin, and salicin. A previous genetic analysis of the E. chrysanthemi arb genes, which mediate ,-glucoside metabolism, suggested that they were homologous to the Escherichia coli K-12 bgl genes. We have now determined the nucleotide sequence of a 5,065-bp DNA fragment containing three genes, arbG, arbF, and arbB. Deletion analysis, expression in minicell systems, and comparison with sequences of other proteins suggest that arbF and arbB encode a ,3-glucoside-specific phosphotransferase system-dependent permease and a phospho-o-glucosidase, respectively. The ArbF amino acid sequence shares 55% identity with that of the E. coli BglF permease and contains most residues thought to be important for a phosphotransferase. One change, however, was noted, since BglF Arg-625, presumably involved in phosphoryl transfer, was replaced by a Cys residue in ArbF. An analysis of the ArbB sequence led to the definition of a protein family which contained enzymes classified as phospho-,-glucosidases, phospho-I8-galactosidases, I-glucosidases, and j8-galactosidases and originating from gram-positive and gram-negative bacteria, archebacteria, and mammals, including humans. An analysis of this family allowed us (i) to speculate on the ways that these enzymes evolved, (ii) to identify a glutamate residue likely to be a key amino acid in the catalytic activity of each protein, and (iii) to predict that domain II of the human lactate-phlorizin hydrolase, which is involved in lactose intolerance, is catalytically nonactive. A comparison between the untranslated regions of the E. chrysanthemi arb cluster and the E. coli bgl operon revealed the conservation of two regions which, in the latter, are known to terminate transcription under noninducing conditions and be the target of the BgIG transcriptional antiterminator under inducing conditions. ArbG was found to share a high level of similarity with the Bg1G antiterminator as well as with Bacillus subtilis SacT and SacY antiterminators, suggesting that ArbG functions as an antiterminator in regulating the expression of the E. chrysanthemi arb genes.

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The configurations at the anomeric carbon of the reaction products of some digestive carbohydrases

Cited by 31 publications

References 23 publications

Regional distant sequence homology between amylases, α‐glucosidases and transglucanosylases

Regional distant sequence homology between amylases, α‐glucosidases and transglucanosylases

Substrate specificity of small‐intestinal lactase

Nucleotide sequences of the arb genes, which control beta-glucoside utilization in Erwinia chrysanthemi: comparison with the Escherichia coli bgl operon and evidence for a new beta-glycohydrolase family including enzymes from eubacteria, archeabacteria, and humans

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