ᴅ-Glutamatoxydase aus der Antennendrüse des Flußkrebses Orconectes limosus: Reinigung und Charakterisierung

Abstract

An enzyme that oxidizes ᴅ-glutamate and ᴅ-aspartate has been partially purified from the antennal gland of the crayfish. The enzyme is inactivated by dialysis against buffered potassium bromide; the activity is restored by adding FAD, but not by FMN. The enzyme is strictly specific for ᴅ-glutamate and D-aspartate and inactive on all tested ᴅ-amino-monocarboxylic acids and glycine. In pure oxygen the activity is about 20 to 30% higher than in air. The enzyme does not use ferricyanide as acceptor. The pH optimum is reached at pH 9,0 to 9,5. At pH 8,6 the Km for D-glutamate is 15,2·10-3 Μ, for D-aspartate 5,4·10-3Μ. The Vmax with D-glutamate is 50% higher than with D-aspartate. Accordingly the enzyme should be named D-glutamate: oxygen oxidoreductase (deaminating). Because of the different values of Km the activity on D-aspartate is higher than that on D-glutamate at substrate concentrations below 20 mM. The enzyme is inhibited by Veronal, p-chloromercuribenzoate, iodoacetamide and to a certain degree by ʟ-glutamate and L-aspartate, but not by benzoate, iodoacetate and the dicarboxylic acids α-oxoglutarate, succinate and oxalacetate. The enzyme is compared with the D-glutamate oxidase from Octopus hepatopancreas and the D-aspartate oxidase from rabbit kidney.