Purification and characterization of citrate synthase isoenzymes from Pseudomonas aeruginosa

Two types of citrate synthase (CS) have been purified from Pseudomonas aeruginosa, a 'large' form (CSI) and a 'small' form (CSII). The M(r)s of the CSI and CSII isoenzymes were determined to be 240,000 +/- 16,000 (mean +/- S.E.M.) and 80,300 +/- 3800 respectively. Chemical cross-linking of the native enzymes with either dimethyl suberimidate or glutaraldehyde followed by electrophoretic analysis by SDS/PAGE showed that CSI is a hexamer and CSII is a dimer. SDS/PAGE showed that CSI and CSII each consist of a single subunit type, of M(r) 42,000 +/- 2000 and M(r) 36,500 +/- 2000 respectively. CSI and CSII were also shown to be distinct kinetically, immunologically and in terms of their regulatory properties. It is suggested that the CS isoenzymes are products of different structural genes.