A novel L-glutamate oxidase from Streptomyces endus. Purification and properties.
A new flavoenzyme using molecular oxygen to oxidize L-glutamic acid has been purified to homogeneity, as judged by polyacrylamide gel electrophoresis, from the culture medium of Streptomyces endus. Hydrogen peroxide, 2-oxoglutaric acid and ammonia are formed as products. Among 25 amino acids tested including D-glutamic acid, L-glutamine and L-aspartic acid, only L-glutamic acid is converted. The molecular mass of the enzyme was estimated to be about 90 kDa by gel chromatography and 50 kDa by SDS/PAGE. The subunit contains 1 molecule noncovalently bound FAD. The absorption spectrum shows maxima at 273, 355 and 457 nm and the isoelectric point is at pH 6.2. The Km value for L-glutamic acid in air-saturated phosphate pH 7.0 was estimated to be 1.1 mM, the Km for oxygen was calculated to be 1.86 mM at saturating concentration of L-glutamic acid. The enzymic reaction is inhibited by Ag+ and Hg2+ ions. The enzyme described here distinctly differs from two microbial L-glutamate oxidases purified hitherto, with regard to extremely high substrate specificity and to the subunit structure.
Böhmer
A
A
Department of Enzymology, Central Institute of Molecular Biology of the Academy of Sciences, German Democratic Republic, Berlin.
Müller
A
A
Passarge
M
M
Liebs
P
P
Honeck
H
H
Müller
H G
HG
D000594:Amino Acid Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007700:Kinetics; D013053:Spectrophotometry; D013302:Streptomyces / Q000201:enzymology* / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
D000594:Amino Acid Oxidoreductases; C023061:L-glutamate oxidase