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)

(1,3)-beta-D-Glucan synthase of Candida albicans was rendered soluble by treatment of membrane preparations with the polyoxyethylene ether detergent W-1. Extraction with 0.025% W-1 at 4 degrees C for 24 h effectively solubilized and activated the enzyme. Under these conditions, greater than 85% of the protein in membrane preparations was released, and about 64% of the glucan synthase activity could be recovered in the soluble form. Soluble enzyme activity was stable for more than 12 days at 4 degrees C. Also, glucan synthase activity in the extracted membrane preparations could be activated to achieve more than twice the enzyme activity in the original, unextracted membrane preparations. The soluble glucan synthase had characteristics similar to those of the membrane-bound enzyme. Soluble glucan synthase had an apparent Km of 2.0 mM, and particulate glucan synthase had an apparent Km of 2.5 mM. Kinetics of cilofungin inhibition for both enzyme preparations were noncompetitive, with an apparent Ki of 2.5 microM; both preparations could be inhibited by cilofungin but not by its peptide nucleus or side chain, either alone or in combination. The reaction products from both forms of the enzyme were sensitive to (1,3)-beta-D-glucanase degradation but not to alpha-amylase, alpha-glucosidase, or proteinase K degradation and thus were shown to be beta(1----3) glucan.
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PMID:W-1 solubilization and kinetics of inhibition by cilofungin of Candida albicans (1,3)-beta-D-glucan synthase. 182 95

Bacteroides thetaiotaomicron can utilize amylose, amylopectin, and pullulan as sole sources of carbon and energy. The enzymes that degrade these polysaccharides were found to be primarily cell associated rather than extracellular. Although some activity was detected in extracellular fluid, this appeared to be the result of cell lysis. The cell-associated amylase, amylopectinase, and pullulanase activities partitioned similarly to the periplasmic marker, acid phosphatase, when cells were exposed to a cold-shock treatment. Two other enzymes associated with starch breakdown, alpha-glucosidase and maltase, appeared to be located in the cytoplasm. Intact cells of B. thetaiotaomicron were found to bind 14C-starch. Binding was probably mediated by a protein because it was saturable and was decreased by treatment of cells with proteinase K. Results of competition experiments showed that the starch-binding proteins had a preference for maltodextrins larger than maltohexaose and a low affinity for maltose and maltotriose. Both the degradative enzymes and starch binding were induced by maltose. These findings indicate that starch utilization by B. thetaiotaomicron apparently does not involve secretion of extracellular enzymes. Rather, binding of the starch molecule to the cell surface appears to be a first step to passing the molecule through the outer membrane and into the periplasmic space.
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PMID:Biochemical evidence that starch breakdown by Bacteroides thetaiotaomicron involves outer membrane starch-binding sites and periplasmic starch-degrading enzymes. 272 47

Ruminobacter amylophilus is an obligate anaerobe that uses only alpha-linked glucose molecules (i.e., maltose, maltodextrins, and starch) as a source of energy, making it an excellent model for the study of bacterial starch degradation. Constitutive amylase, amylopectinase, and pullulanase activities were found in intracellular and extracellular fractions of R. amylophilus. However, extracellular activities apparently resulted from cell lysis. Both soluble and membrane-bound polysaccharidase activities were detected. Most of the soluble polysaccharidase activity partitioned with the periplasmic cell fraction. No alpha-glucosidase or maltase activity was detected in either the cellular or extracellular fraction. In addition, intact cells of R. amylophilus bound U-14C-starch. This binding could be saturated and was constitutive and sensitive to proteinase K, indicating protein or protein complex mediation. Competition experiments showed that these starch-binding sites had equally high affinities for starch and maltodextrins larger than maltotriose. The sites had a reduced affinity for maltose and virtually no affinities for glucose and nonstarch polysaccharides. These findings suggest that R. amylophilus binds starch molecules to the cell surface as an initial step in transporting the molecule through the outer membrane and into the periplasmic space. Extracellular polysaccharides do not appear to be involved in starch degradation.
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PMID:Biochemical analysis of starch degradation by Ruminobacter amylophilus 70. 753 78