GudB seems to be intrinsically inactive, however spontaneous mutations removing a 9-bp direct repeat within the wild-type gudB sequence activated the GudB protein and allowed more-efficient utilization of amino acids of the glutamate family (called gutB1). This 3 amino acid insertion presumably causes severe destabilization of the fold of the protein, leading to an inactive enzyme that is very quickly degraded. The cryptic GudB serves as a buffer that may compensate for mutations in the rocG gene and that can also be decryptified for the utilization of glutamate as a single carbon source in the absence of arginine. It is unable to synthesize glutamate. H2O + L-glutamate + NAD(+) = 2-oxoglutarate + H(+) + NADH + NH4(+) Homohexamer. Constitutively expressed. No visible phenotype. Cells lacking this gene show no growth defect; a double rocG-gudB disruption has the same phenotype as a single rocG disruption. Belongs to the Glu/Leu/Phe/Val dehydrogenases family.