PMID: 6112982Nov 1, 1980Paper

Active-site modification of native and mutant forms of inosine 5'-monophosphate dehydrogenase from Escherichia coli K12

The Biochemical Journal
H J Gilbert, W T Drabble

Abstract

IMP dehydrogenase of Escherichia coli was irreversibly inactivated by Cl-IMP (6-chloro-9-beta-d-ribofuranosylpurine 5'-phosphate, 6-chloropurine ribotide). The inactivation reaction showed saturation kinetics. 6-Chloropurine riboside did not inactivate the enzyme. Inactivation by Cl-IMP was retarded by ligands that bind at the IMP-binding site. Their effectiveness was IMP>XMP>GMP>AMP. NAD(+) did not protect the enzyme from modification. Inactivation of IMP dehydrogenase was accompanied by a change in lambda(max.) of Cl-IMP from 263 to 290nm, indicating formation of a 6-alkylmercaptopurine nucleotide. The spectrum of 6-chloropurine riboside was not changed by IMP dehydrogenase. With excess Cl-IMP the increase in A(290) with time was first-order. Thus it appears that Cl-IMP reacts with only one species of thiol at the IMP-binding site of the enzyme: 2-3mol of Cl-IMP were bound per mol of IMP dehydrogenase tetramer. Of ten mutant enzymes from guaB strains, six reacted with Cl-IMP at a rate similar to that for the native enzyme. The interaction was retarded by IMP. None of the mutant enzymes reacted with 6-chloropurine riboside. 5,5'-Dithiobis-(2-nitrobenzoic acid), iodoacetate, iodoacetamide and methyl methanethiosulphonate also i...Continue Reading

Citations

Jan 1, 1984·Molecular & General Genetics : MGG·M S Thomas, W T Drabble
Dec 11, 2020·Antiviral Chemistry & Chemotherapy·Johanna Huchting
Jun 2, 2009·Chemical Reviews·Lizbeth Hedstrom
Nov 6, 1987·Biochimica Et Biophysica Acta·J D PageD J Holbrook
Jun 1, 1993·Comparative Biochemistry and Physiology. B, Comparative Biochemistry·M E Pugh, E B Skibo

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