Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A technique for the isolation of intact brush borders from rabbit renal cortex was evaluated. The procedure was monitored by phase and electron microscopy and marker enzymes, i.e. ATP:NMN adenylyl transferase, nuclear; cytochrome oxidase, mitochondrial; beta-glucuronidase, lysosomal; and glucose-6-Pase, microsomal; and indicated an essentially pure preparation of brush borders. The disaccharidase, trehalase, previously reported in renal tubules, was localized uniquely in brush borders. Maltase was also found; the specific activities of the two enzymes in the brush borders were increased 10- to 20-fold. Other disaccharidases, such as sucrase, isomaltase, lactase, and cellobiase, were absent. It is suggested that trehalase and maltase are appropriate candidates for marker enzymes of the renal brush border. Isolated brush borders possessed a ouabain-sensitive (Na(+) + K(+)) ATPase, an oligomycin-insensitive Mg(++) ATPase, and a Ca(++)-activated ATPase. Alkaline phosphatases, dephosphorylating beta-glycero-P, and trehalose-6-P were also present. The specific activities of these enzymes were increased three-to-five fold in the brush-border preparations; however, activities were found in other subcellular fractions of the renal cortex. Hexokinase, although evident in the isolated brush border, was found prominently associated with other membranous fractions. Phosphoglucomutase and UDPG pyrophosphorylase were localized in the soluble fraction of the renal cortex.
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PMID:Isolation and biochemical characterization of brush borders from rabbit kidney. 425 Jun 12

Maltose metabolism was investigated in the hyperthermophilic archaeon Thermococcus litoralis. Maltose was degraded by the concerted action of 4-alpha-glucanotransferase and maltodextrin phosphorylase (MalP). The first enzyme produced glucose and a series of maltodextrins that could be acted upon by MalP when the chain length of glucose residues was equal or higher than four, to produce glucose-1-phosphate. Phosphoglucomutase activity was also detected in T. litoralis cell extracts. Glucose derived from the action of 4-alpha-glucanotransferase was subsequently metabolized via an Embden-Meyerhof pathway. The closely related organism Pyrococcus furiosus used a different metabolic strategy in which maltose was cleaved primarily by the action of an alpha-glucosidase, a p-nitrophenyl-alpha-D-glucopyranoside (PNPG)-hydrolyzing enzyme, producing glucose from maltose. A PNPG-hydrolyzing activity was also detected in T. litoralis, but maltose was not a substrate for this enzyme. The two key enzymes in the pathway for maltose catabolism in T. litoralis were purified to homogeneity and characterized; they were constitutively synthesized, although phosphorylase expression was twofold induced by maltodextrins or maltose. The gene encoding MalP was obtained by complementation in Escherichia coli and sequenced (calculated molecular mass, 96,622 Da). The enzyme purified from the organism had a specific activity for maltoheptaose, at the temperature for maximal activity (98 degrees C), of 66 U/mg. A Km of 0.46 mM was determined with heptaose as the substrate at 60 degrees C. The deduced amino acid sequence had a high degree of identity with that of the putative enzyme from the hyperthermophilic archaeon Pyrococcus horikoshii OT3 (66%) and with sequences of the enzymes from the hyperthermophilic bacterium Thermotoga maritima (60%) and Mycobacterium tuberculosis (31%) but not with that of the enzyme from E. coli (13%). The consensus binding site for pyridoxal 5'-phosphate is conserved in the T. litoralis enzyme.
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PMID:Maltose metabolism in the hyperthermophilic archaeon Thermococcus litoralis: purification and characterization of key enzymes. 1034 46

The objectives of this study were to examine the effects of growth substrate and extracellular pH on phosphoenolpyruvate-dependent glucose phosphorylation as well as to examine how maltose is phosphorylated by the ruminal bacterium Megasphaera elsdenii B159. Phosphoenolpyruvate-dependent glucose phosphorylation by toluene-treated cells was constitutive, and glucose phosphorylation was reduced by 69% at pH 5.0. When toluene-treated cells were incubated in histidine buffer, little maltose phosphorylation occurred in the absence of inorganic phosphate. However, the addition of increasing concentrations of either potassium or sodium phosphate increased maltose phosphorylation. Maximal phosphorylation activity was observed at between 25 and 50 mM of either inorganic phosphate source. Compared with the control incubations, maltose phosphorylation was increased over threefold with 25 mM of either potassium or sodium phosphate. Phosphoglucomutase activity was detected in cell extracts of M. elsdenii B159, and this enzyme had a K(m) of 3.2 mM for glucose-1-P and a V(max) of 1836 nmol of NADP(+) reduced/mg of protein per min. Maltose was also hydrolyzed by an inducible maltase (K(m), 1.19 mM). To our knowledge, this is the first report of a maltose phosphorylase and a maltase in M. elsdenii.
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PMID:Factors affecting glucose and maltose phosphorylation by the ruminal bacterium Megasphaera elsdenii. 1082 81