An improved method for determination of N-acetyl-L-glutamate by its function as an activator of carbamoyl phosphate synthetase I.
N-Acetyl-L-glutamate has been examined with regard to its ability to activate carbamoyl phosphate synthetase I (EC 6.3.4.16). Substance(s) inhibitory to carbamoyl phosphate synthetase, present even in the partially purified preparation of rat liver extracts, interfered with the measurement of acetylglutamate. In the experiments using chelating agents, metals were apparently involved in this inhibition. When the partially purified preparation of liver extract was placed on a Chelex 100 column, the inhibitor was eliminated and accurate measurements of acetylglutamate content could be made. Evidence supporting the validity of this improved method is given. A significant difference was observed between acetylglutamate levels determined by the present method and by the one using aminoacylase I (N-acylamino acid amidohydrolase, EC 3.5.1.14) to hydrolyze acetylglutamate followed by assay of the glutamate generated. We searched for the presence of glutamate derivatives other than acetylglutamate. When impure tissue preparations containing acetylglutamate were treated with a commercial preparation of aminoacylase, there was an excess amount of glutamate apparently derived from compounds other than acetylglutamate. This can lead to an overestimation of the tissue levels of acetylglutamate.
Sonoda
T
T
Department of Biochemistry, Chiba University School of Medicine, Japan.
Tatibana
M
M
D000818:Animals; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000378:metabolism*; D002854:Chromatography, Paper; D004789:Enzyme Activation; D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates / Q000032:analysis* / Q000378:metabolism; D008099:Liver / Q000032:analysis / Q000201:enzymology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing); C016195:N-acetylglutamic acid