A new type of membrane-bound oxidoreductase is described that carries out an oxidative deamination reaction that specifically involves L-glutamate. This enzyme is found in a subcellular fraction of Azotobacter vinelandii strain 0. It can oxidize L-(+)-glutamate using molecular oxygen and produces α-ketoglutarate and NH3 as end products. Neither NAD+ nor NADP+ are involved in this oxidation. The reaction is carried out by the membranous "R3" fraction which is obtained from sonically ruptured resting cells by differential centrifugation. In addition to O2, the electron acceptors that allowed for L-glutamate oxidation were phenazine methosulfate (PMS), K3Fe(CN)6, and 2, 6-dichloroindophenol (DCIP). This oxidation appears to be an integral part of the Azotobacter electron transport system as the L-glutamate oxidase rate is also highly sensitive to known electron transport inhibitors, i.e., 2-n-hydroxy-4-quinoline-N-oxide, cyanide, and thenoyltrifluoroacetone. Spectral absorption studies on the Azotobacter R3 electron transport fraction revealed that the cytochrome and flavoprotein (non-heme iron) components also could be reduced completely upon the addition of L-glutamate. Preliminary results suggest that this is a new type of L-glutamate oxidoreductase that does not as yet have an Enzyme Commission number and appears to be (a) a specific flavoprotein enzyme that is not a type of L-amino acid oxidase, (b) tightly bound (and functionally attached) to the Azotobacter electron transport system, and (c) capable of carrying out specifically the oxidative deamination of L-glutamate in the absence of pyridine nucleotides.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)