AZOTOBACTER-VINELANDII CITRATE SYNTHASE

We have purified the citrate synthase from Azotobacter vinelandii and have determined that the size of the subunit is 48 000 Da and the stru cture of the holoenzyme is a hexamer. This contrasts with earlier esti mates that indicate a 58 000 Da subunit and a tetrameric structure. In addition, the enzyme is allosteric with a Hill coefficient of 1.5 and is inhibited by NADH. The Hill coefficient is changed to about 1 by h igh ionic strength and AMP. The enzyme is thus similar to the citrate synthases of many other Gram-negative, facultative, anaerobic organism s. In addition, the amino acid sequence of about 100 residues has been determined and found to be highly similar to the sequence of Pseudomo nas aeruginosa citrate synthase.