Abstract
Triethylenetetramine (TETA) is an efficient copper chelator having versatile clinical potential. We have recently shown that spermidine/spermine-N1-acetyltransferase (SSAT1), the key polyamine catabolic enzyme, acetylates TETA in vitro. Here, we studied the metabolism of TETA in three different mouse lines: syngenic, SSAT1 overexpressing and SSAT1-deficient (SSAT1-KO) mice. The mice were sacrificed at 1, 2 or 4 hours after TETA injection (300 mg/kg i.p.). We found only N1-acetyltriethylentetramine (N1AcTETA) and/or TETA in the liver, kidney and plasma samples. As expected, SSAT1 overexpressing mice acetylated TETA at an accelerated rate as compared to syngenic and SSAT1-KO mice. Interestingly, SSAT1-KO mice metabolized TETA as syngenic mice did, probably by thialysine acetyltransferase, which had Km of 2.5 ± 0.3 mM and kcat of 1.3 s-1 for TETA when tested in vitro with the human recombinant enzyme. Thus, the present results suggest that there are at least two N-acetylases potentially metabolizing TETA. However, their physiological significance for TETA acetylation requires further studies. Furthermore, we detected chemical intramolecular N-acetyl migration from N1- to N3-position of N1AcTETA and N1,N8-diacetyltriethylenetetramine in acidified HPLC sample matrix. The complex metabolism of TETA together with the intramolecular N-acetyl migration may explain the huge individual variations in the acetylation rate of TETA reported earlier.
- acetylation
- acetyltransferases
- analytical chemistry
- enzyme induction
- HPLC
- mass spectrometry
- metabolite identification
- Received July 13, 2011.
- Accepted August 30, 2011.
- The American Society for Pharmacology and Experimental Therapeutics