Possible physiological roles of aspartase, NAD- and NADP-requiring glutamate dehydrogenases of Pseudomonas fluorescens.

The levels of aspartase, NADP- and NAD-requiring glutamate dehydrogenases (GDHs) in Pseudomonas fluorescens grown under various nutritional conditions were determined. NADP-GDH showed the highest value on glucose-ammonium sulfate medium and markedly lower values on amino-acid and casamino-acids media, while the reverse was found for the NAD-GDH, as in the case of other microorganisms with two GDHs. Aspartase did not show a marked variation between the media examined. Glucose nutritionally induced NADP-GDH but suppressed NAD-GDH; and it had no effect on aspartase, which was slightly induced by casamino acids. Transfer of the cells grown on glucose-ammonium sulfate medium to casamino-acids medium clearly increased the levels of NAD-GDH and aspartase, while addition of chloramphenicol to the media abolished the increases, suggesting that the increases were due to de novo synthesis of the enzyme proteins. These results indicate that the aspartase of this microorganism has a different function from those in others, including Escherichia coli.