Acid-induced change in ozone-reactive site in indole ring of tryptophan.
It is well established that ozone as well as oxygen activated by tryptophan 2,3-dioxygenase or indoleamine 2,3-dioxygenase cleave the 2,3-C=C bond of the indole ring of tryptophan to produce N-formylkynurenine. In the present study, however, we found that exposure of tryptophan to aqueous ozone at and below pH 4.5 generated a different compound. The compound was identified as kynurenine by high performance liquid chromatography and mass spectrometry. Exposure of N-formylkynurenine to acidic ozone did not generate a significant amount of kynurenine, indicating that the kynurenine was not produced via N-formylkynurenine. Acidic ozone thus appears to cleave the 1, 2-NAC bond in place of the 2,3-C=C bond of the indole ring, followed by liberation of the 2-C atom. The 1,2-NAC bond and 2,3-C=C bond are likely to undergo changes in their nature of bonding on acidification, enabling ozone to react with the former bond but not with the latter bond.
Matsumura
Sueo
S
Department of Pathema Analysis, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma, Kobe 645-0142, Japan. matsmura@kobe-u.ac.jp
Yoshimura
Ayuko
A
Okazaki
Kazuyuki
K
Fijitani
Noboru
N
Hattori
Hideki
H
D000143:Acids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000737:chemistry*; D007737:Kynurenine / Q000031:analogs & derivatives* / Q000737:chemistry; D010126:Ozone / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry*
D000143:Acids; D007211:Indoles; C007772:N'-formylkynurenine; D007737:Kynurenine; D010126:Ozone; C030374:indole; D014364:Tryptophan