Occurrence of cold-labile NAD-specific glutamate dehydrogenase in Bacillus species

Abstract

A nicotinamide adenine dinucleotide-specific glutamate dehydrogenase (NAD-GluDH; EC 1.4.1.3) inactivated by incubation at low temperatures was detected in several species of the genus Bacillus, including strains of B. cereus, B. laterosporus, B. lentus, B. panthotenicus, B. pasteurii, B. sphaericus, B. stearothermophilus, B. subtilis and B. thuringiensis. Incubation of cell-free extracts of these strains at 0 degrees C resulted in an 80-100% inactivation of NAD-GluDH activity within 120 min. The addition of 20% glycerol protected the enzyme from this inactivation in the cold. Strains of B. fastidiosus, B. licheniformis, B. macerans, B. megaterium and B. pumilus were found to lack NAD-GluDH activity.

Molecular Properties and Enhancement of Thermostability by Random Mutagenesis of Glutamate Dehydrogenase fromBacillus subtilis

“…Conflicting reports on the presence or absence of NAD-dependent GluDH in Bacillus strains a decade ago might have been due to the extremely rapid loss of activity of the enzyme in the cold. 30) Protein concentration did not affect the loss of enzyme activity of NAD-dependent GluDH from B. cereus DSM 31 in the cold, and no reactivation of the enzyme was observed upon incubation of cold-inactivated cell-free extract at 30 C for 5 min. 31) On the other hand, the unfolding of the protein structure of GluDH from B. acidocaldarius at higher concentrations of GuHCl underwent refolding when the unfolded mixture was diluted.…”

Isolation of a novel, phosphate-activated glutaminase from Bacillus pasteurii

“…Since no L-glutamine transaminase/g-amidase activity was detected in this organism (data not shown), and since L-glutamine has been shown to serve as a carbon source for growth [6], this glutaminase obviously functions as a catabolic enzyme providing L-glutamate for further oxidation. The identi¢-cation of two di¡erent glutamate dehydrogenases [30] completes the degradation pathway of glutamine in B. pasteurii, a pathway starting with the sodium-dependent active transport of glutamine in this alkaliphile [8]. The speci¢c activity with L-glutamine as substrate was set as 100%.…”

Isolation of a novel, phosphate-activated glutaminase fromBacillus pasteurii

“…Since no l ‐glutamine transaminase/ω‐amidase activity was detected in this organism (data not shown), and since l ‐glutamine has been shown to serve as a carbon source for growth [6], this glutaminase obviously functions as a catabolic enzyme providing l ‐glutamate for further oxidation. The identification of two different glutamate dehydrogenases [30] completes the degradation pathway of glutamine in B. pasteurii , a pathway starting with the sodium‐dependent active transport of glutamine in this alkaliphile [8].…”