Metabolism of triacetone triperoxide (TATP) by canine cytochrome P450 2B11
This work is performed to determine if there is a potential for the accumulation and potential toxicity of triacetone triperoxide (TATP) in canines. Additional utility of this information may suggest human toxicity and possibly detection of biomarkers, metabolites or intact molecule of those using this material for nefarious reasons.
Liquid chromatography/mass spectrometry of dog liver microsome (DLM) incubation samples of TATP was used to measure substrate depletion. Trapping of electrophilic products was performed using glutathione (GSH) and semicarbazide. Comparisons were made to free hydroperoxides found in methyl ethyl ketone peroxides (MEKP).
The non-specific Km value of 2.2 μM and a Vmax of 1.1 nmol/min/mg of protein were determined. Canine recombinant cytochrome P450 (rCYP) 2B11 with human cytochrome b5 was found to catalyze the NADPH-dependent metabolism of TATP into its only phase I metabolite, hydroxy-TATP (TATP-OH). No secondary metabolite(s) or degraded products were detected or trapped from microsomal incubations. MEKP subjected to similar conditions was found to undergo significant metabolism, semicarbazide trapping and rapid oxidation of GSH to GSSG. The synthesized TATP-OH metabolite incubated in DLM progressed three times faster than TATP metabolism with no secondary metabolites found or trapped.
TATP does not react as MEKP suggesting that TATP does not ring-open to form hydroperoxides. TATP and TATP-OH compete for the same enzyme, with TATP dominating this competition. Failure to detect additional metabolite(s) suggests they may be too small to detect by our system or bound covalently to a protein or polymer in the incubation reaction.
KeywordsTATP metabolism/conversion CYP2B11 Cytochrome b5 Peroxide metabolism Metabolite synthesis Toxicity
This material is based upon work supported by U.S. Department of Homeland Security (DHS), Science & Technology Directorate, Office of University Programs, under Grant 2013-ST-061-ED0001. Views and conclusions are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of DHS.
Compliance with ethical standards
Conflict of interest
The authors have no conflict of interest to declare.
Samples produced using human cytochrome b5 or human reductase bactosomes are not recovered from any human patients and are not subject to human biological sample management required by GxP.
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