ALKYLATION OF ISOCITRATE LYASE FROM ESCHERICHIA-COLI BY 3-BROMOPYRUVATE

The inactivation of tetrameric isocitrate lyase from Escherichia coli by 3-bromopyruvate, exhibiting saturation kinetics, is accompanied by the loss of one sulfhydryl per subunit. The substrates glyoxylate and isocitrate protect against inactivation whereas the substrate succinate does not. The modification by 3-bromopyruvate (equimolar to subunits) imparts striking resistance to digestion of isocitrate lyase by trypsin, chymotrypsin, and V8 protease as well as a major decrease in the intensity of tryptophan fluorescence. After alkylation, the sequence GlyHisMetGlyGlyLys is found following the modified Cys residue in the tryptic peptide representing positions 196-201. Thus Cys195 is alkylated by 3-bromopyruvate. © 1990.