Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The thermophilic 6-phosphogluconate dehydrogenase from Bacillus stearothermophilus was inhibited upon specific modification of the -SH group of cysteine residues by 7-chloro-4-nitrobenzo-2-oxa-1, 3-diazole (NBD-Cl) at pH 7.0. By using 20-100-fold molar excess of NBD-CL the reaction occurs slowly at pH 7.0 as a first order process. Partial protection from inactivation was observed when the substrate 6-phosphogluconate or the coenzyme NADP was added to the reaction mixture. Complete inactivation was achieved upon modification of 1.9 of the six cysteine residues per mole of enzyme, which corresponds to nearly one residue per enzyme subunit. Circular dichroism measurements suggest that the gross structure of the protein molecule is practically unchanged upon reaction of the enzyme with NBD-Cl. Melting profile experiments revealed a single transition occurring at about 65 degrees C. Analogously, the profile of intensity of the fluorescence emission at 520 nm of the enzyme-bound S-NBD groups versus temperature indicated a midpoint of transition near 65 degrees C. Since this melting temperature corresponds closely to that observed with the native enzyme, these results would indicate that the molecular organizations of the native and modified enzyme are similar and stabilized by similar interactions within the polypeptide chain.
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PMID:Fluorescent labelling of 6-phosphogluconate dehydrogenase from Bacillus stearothermophilus. 1 68

Using stepwise protein fractionation by (NH4)2SO4 and ion-exchange chromatography on CM-cellulose, DEAE-cellulose and SP-Sephadex, two isoforms of 6-phosphogluconate dehydrogenase, A and B, from rat liver were obtained. The method developed allows to achieve complete separation of these forms and to obtain preparative amounts of the protein with specific activities of 5.7 and 10.7, respectively. The native enzyme forms A and B have molecular weights of 107000 and are represented by dimers composed of subunits with identical molecular weights equal to 54000. Both isoforms have a pH optimum at 8.5 and reveal different sensitivity to MgCl2 and MnCl2. The tetrahedron-shaped ions (phosphate, molibdate, arsenate) inhibit the both molecular forms of the enzyme, The Arrhenius plots for the reaction rate are uninterrupted lines within the temperature range of 21-44 degrees; the values of activation energy and the temperature coefficient for isoforms A and B are 12750 and 13500 cal/mole and 2.05 and 2.15, respectively.
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PMID:[Purification and some properties of molecular forms of 6-phosphogluconate dehydrogenase from rat liver]. 715 26