Characterization of Glutathione Transferase from Xanthomonas campestris

A single form of glutathione transferase (Xc-GST-4.5) having an isoelectric point at pH 4.5 was resolved from Xanthomonas campestris cytosol by affinity chromatography and isoelectric focusing. HPLC, N-terminal amino acid sequence, and SDS-PAGE analyses indicate that Xc-GST-4.5 is composed of two identical subunits, each with a molecular mass of 22 kDa. As indicated by its substrate specificity, immunological reactivity, and CD spectra, as well as by its N-terminal amino acid sequence, Xc-GST-4.5 appears to be distinct from the other bacterial glutathione transferases, Pm-GST-6.0 and Sm-GST-7.3, previously purified from the cytosolic fraction of Proteus mirabilis and Serratia marcescens. Xc-GST-4.5 also appears to be distinct from the GST so far purified from other sources.