title: Measurement of (15)N enrichment of glutamine and urea cycle amino acids derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate using liquid chromatography-tandem quadrupole mass spectrometry.
abstract: 6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) is an amino acid-specific derivatizing reagent that has been used for sensitive amino acid quantification by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). In this study, we aimed to evaluate the ability of this method to measure the isotopic enrichment of amino acids and to determine the positional (15)N enrichment of urea cycle amino acids (i.e., arginine, ornithine, and citrulline) and glutamine. The distribution of the M and M+1 isotopomers of each natural AQC-amino acid was nearly identical to the theoretical distribution. The standard deviation of the (M+1)/M ratio for each amino acid in repeated measurements was approximately 0.1%, and the ratios were stable regardless of the injected amounts. Linearity in the measurements of (15)N enrichment was confirmed by measuring a series of (15)N-labeled arginine standards. The positional (15)N enrichment of urea cycle amino acids and glutamine was estimated from the isotopic distribution of unique fragment ions generated at different collision energies. This method was able to identify their positional (15)N enrichment in the plasma of rats fed (15)N-labeled glutamine. These results suggest the utility of LC-MS/MS detection of AQC-amino acids for the measurement of isotopic enrichment in (15)N-labeled amino acids and indicate that this method is useful for the study of nitrogen metabolism in living organisms.
authors: Institute for Innovation, Ajinomoto, Kawasaki-ku, Kawasaki-shi 210-8681, Japan.
authors: Hidehiro
authors: H
authors: Nakamura
authors: Institute for Innovation, Ajinomoto, Kawasaki-ku, Kawasaki-shi 210-8681, Japan.
authors: Sachise
authors: S
authors: Karakawa
authors: Institute for Innovation, Ajinomoto, Kawasaki-ku, Kawasaki-shi 210-8681, Japan.
authors: Akiko
authors: A
authors: Watanabe
authors: Institute for Innovation, Ajinomoto, Kawasaki-ku, Kawasaki-shi 210-8681, Japan.
authors: Yasuko
authors: Y
authors: Kawamata
authors: Institute for Innovation, Ajinomoto, Kawasaki-ku, Kawasaki-shi 210-8681, Japan.
authors: Tomomi
authors: T
authors: Kuwahara
authors: Institute for Innovation, Ajinomoto, Kawasaki-ku, Kawasaki-shi 210-8681, Japan.
authors: Kazutaka
authors: K
authors: Shimbo
authors: Institute for Innovation, Ajinomoto, Kawasaki-ku, Kawasaki-shi 210-8681, Japan. Electronic address: ryosei_sakai@ajinomoto.com.
authors: Ryosei
authors: R
authors: Sakai
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D000634:Aminoquinolines / Q000737:chemistry*; D000818:Animals; D002219:Carbamates / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000379:methods*; D005973:Glutamine / Q000737:chemistry*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: C078178:6-aminoquinolyl-N-hydroxysuccinimidyl carbamate; D000596:Amino Acids; D000634:Aminoquinolines; D002219:Carbamates; D005973:Glutamine
keywords: Isotopic enrichment; LC–MS/MS; Urea cycle amino acids