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Glutamine: precursor or nitrogen donor for the synthesis of citrulline?
Author(s) -
Marini Juan C,
Didelija Inka Cajo,
Castillo Leticia,
Lee Brendan
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.740.14
Subject(s) - chemistry , glutamine , citrulline , ammonium , arginine , proline , nitrogen , stereochemistry , biochemistry , amino acid , organic chemistry
Glutamine (Gln) is considered the main precursor for citrulline (Cit) synthesis, but no attempts have been made to differentiate the contribution of Gln carbon (Gln‐C) skeleton vs. the nonspecific contribution through NH 3 and CO 2 . To study the contribution of dietary Gln‐N to the synthesis of Cit, the incorporation of 2‐ 15 N and 5‐ 15 N Gln, and 15 N ammonium into the 3 N groups of Cit was determined in conscious mice. D 5 and U‐ 13 C 5 Gln were used to determine the incorporation of Gln‐C. The contribution of dietary arginine (Arg) and proline (Pro) were also determined by the infusion of U‐ 13 C n tracers. The 2‐ 15 N Gln tracer labeled to a similar extent the 3 N positions of Cit, while 5‐ 15 N Gln and 15 N ammonium tracers mainly labeled the ureido group. The total incorporation of 2‐ 15 N and 5‐ 15 N exceeded 25‐fold the incorporation of the D 5 tracer. Dietary Arg was the main precursor for Cit synthesis (40% of RaCit), followed by Pro and Gln (3.4 and 0.4% of RaCit, respectively). The incorporation of a single 13 C into Cit from Gln and Pro, but not from Arg, was detected. This represents the oxidation of Gln and Pro in enterocytes, with the subsequent utilization of 13 CO 2 for the synthesis of carbamylphosphate. In conclusion, Gln is not a carbon skeleton precursor for Cit synthesis, but donates nonspecific N and C for its synthesis. Dietary Arg is the main carbon skeleton precursor for Cit synthesis. Support: USDA 2533771314 and NIH KO1 RR24173.