CITRATE SUBSTITUTES FOR HOMOCITRATE IN NITROGENASE OF A NIFV MUTANT OF KLEBSIELLA-PNEUMONIAE

An organic acid extracted from purified dinitrogenase isolated from a nifV mutant of Klebsiella pneumoniae has been identified as citric acid. H2 evolution by the citrate-containing dinitrogenase is partially inhibited by CO, and by some substrates for nitrogenase. The response of maximum velocities to changes in pH for both the wild-type and the NifV− dinitrogenase was compared. No substantial differences between the enzymes were observed, but there are minor differences. Both enzymes are stable in the pH range 4.8-10, but the enzyme activities dropped dramatically below pH 6.2.© 1990, American Chemical Society. All rights reserved.