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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been shown that sodium dodecyl sulfate (SDS) is capable of forming stable complexes with amylose and that fractionation of short-chain amyloses can be effected by SDS-gel electrophoresis. Using a well-defined smylose fraction (molecular weight 4,000), the thermodynamic parameters pertaining to SDS-amylose interaction have been evaluated by means of frontal gel chromatography. The results are as follows: association constant (K)=5.0 times 10-3-M-minus 1 at 25 degrees (pH 9.4); standard free energy change (delta G degrees)=-5.1 kcal/mole; standard enthalpy change (delta H degrees)=-5.8 kcal/mole; standard entropy change (delta Sdegrees)=-2.3(e.u.) and the maximum number of binding sites for SDS (n)=1. In the presence of 0.5--1 percent SDS, amylose migrates toward the anode upon gel electrophoresis, giving a compact band. High resolution of amylose fractions (released by treatment of amylopectin with debranching enzyme) has been attained using pore-size gradient gel electrophoresis.
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PMID:Gel electrophoresis of amylose in the presence of sodium dodecyl sulfate. 112 25

The amylo-1,6-glucosidase catalytic activity of glycogen debranching enzyme allows it to hydrolyze alpha-D-glucosyl fluoride, in the absence or presence of glycogen or oligosaccharides, releasing equal amounts of fluoride and glucose at rates comparable to those seen with the natural substrates. 2-Deoxy-2-fluoro-alpha-D-glucosyl fluoride is found to be a poor substrate, rather than the covalent inhibitor that would be expected for a glucosidase which catalyzes hydrolysis of the glycosidic linkage with retention of anomeric configuration. In fact, analysis of the glucosidase reaction by NMR reveals that the debranching enzyme hydrolyzes the glycosidic linkage with inversion of configuration, releasing beta-D-glucose from both alpha-glucosyl fluoride and its natural substrate, the phosphorylase limit dextrin. In contrast, its transferase activity necessarily proceeds with retention of configuration. As has been seen with other "inverting" glycosidases, the debranching enzyme releases beta-D-glucose from beta-D-glucosyl fluoride in the presence of oligosaccharides such as maltohexaose and cyclomaltoheptaose but, unlike the others, not in their absence. An intermediate glucosyl-alpha-(1,6)-cyclomaltoheptaose has been detected by NMR analysis. In the presence of a water-soluble carbodiimide, a single mole of glycine ethyl ester is incorporated into each mole of the debranching enzyme, resulting in its inactivation when measured by the combined assay for both transferase and glucosidase activities. Measurement of the latter two activities independently indicates that it is the transferase activity which is inactivated, while the glucosidase activity, measured with alpha-D-glucosyl fluoride as substrate, is unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reassessment of the catalytic mechanism of glycogen debranching enzyme. 199 Nov 22