Effects of deuterium labeling on azido amino acid mutagenicity in Salmonella typhimurium.
The mutagenic effects of azide (N3-) anion in bacterial test systems require the formation of the novel mutagenic metabolite, 3-azido-L-alanine (AZAL). Although the mechanism of AZAL-induced mutagenicity is unknown, subsequent bioactivation of this metabolite appears likely. Earlier studies have shown that other azide-containing amino acids are mutagenic as well. In fact, the mutagenic potency of the synthetic AZAL homologue, L-2-amino-4-azidobutanoic acid (HomoAZAL), was several times that of AZAL. To gain insight into the biochemical processing and mutagenicity of azido amino acids in Salmonella typhimurium, several specifically deuterium-labeled azido amino acids have been prepared and tested for mutagenic potency. In addition, the effect of (aminooxy)acetic acid (AOA) (a potent inhibitor of pyridoxal-dependent processes) on AZAL-induced mutagenesis was examined. The results showed that 2-deuterium substitution of AZAL resulted in a slight increase in mutagenic potency, while AOA treatment resulted in no change in AZAL potency. Taken together these findings did not support the involvement of pyridoxal-dependent processes in AZAL bioactivation. In contrast, deuterium substitution adjacent to the azide group in HomoAZAL and 5-azido-L-norvaline (N3-Norval) resulted in a large decrease in mutagenic potency when compared to the non-deuterium labeled compounds. These observations are consistent with a bioactivation mechanism involving rate-limiting C-H bond cleavage in the formation of the ultimate mutagen. Moreover, this effect of deuterium labeling points to processing of the azide-containing side chain as a key feature in the mutagenic activation mechanism.
Mangold
J B
JB
Medicinal Chemistry Program, School of Pharmacy, University of Connecticut, Storrs.
Du
Y
Y
Mischke
M R
MR
LaVelle
J M
JM
D000409:Alanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001386:Azides / Q000494:pharmacology*; D001711:Biotransformation; D003903:Deuterium; D007553:Isotope Labeling; D009152:Mutagenicity Tests; D009153:Mutagens; D012485:Salmonella typhi / Q000187:drug effects / Q000235:genetics
D001386:Azides; D009153:Mutagens; C039309:azidoalanine; D003903:Deuterium; D000409:Alanine