Studies on a mutant form of Escherichia coli citrate synthase desensitised to allosteric effectors.
Naturally occurring citrate synthases fall into distinct molecular and catalytic types. Gram-negative bacteria produce a 'large' enzyme, allosterically inhibited by NADH and, in the facultative anaerobes such as Escherichia coli, also by 2-oxoglutarate. On the other hand, Gram-positive bacteria and all eukaryotes produce a 'small' citrate synthase which is insensitive to these metabolites. As a complement to structure-function studies we have explored the possibility of genetically altering one type of citrate synthase to the other. By mutagenesis and suitable selection we have succeeded in isolating a mutant of E. coli whose citrate synthase is both 'small' and insensitive to NADH and 2-oxoglutarate. Some characteristics of the enzyme are described. Such mutant enzymes offer a novel approach to the study of citrate synthase, its regulation and its natural diversity.
D000494:Allosteric Regulation; D000495:Allosteric Site; D002950:Citrate (si)-Synthase / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D007656:Ketoglutaric Acids / Q000494:pharmacology; D007700:Kinetics; D009154:Mutation; D009243:NAD / Q000494:pharmacology; D010084:Oxidation-Reduction; D007652:Oxo-Acid-Lyases / Q000378:metabolism*
D007656:Ketoglutaric Acids; D009243:NAD; D002950:Citrate (si)-Synthase; D007652:Oxo-Acid-Lyases