Mutagenesis Advance Access originally published online on December 8, 2006
Mutagenesis 2007 22(1):75-81; doi:10.1093/mutage/gel054
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The stimulatory role of human cytochrome b5 in the bioactivation activities of human CYP1A2, 2A6 and 2E1: a new cell expression system to study cytochrome P450-mediated biotransformation (a corrigendum report on Duarte et al. (2005) Mutagenesis 20, 93–100)
1 Department of Genetics, Faculty of Medical Sciences, Universidade Nova de Lisboa Rua da Junqueira 96, 1349-008 Lisboa, Portugal 2 Faculty of Science and Technology, Universidade Nova de Lisboa Quinta da Torre, 2829-516 Caparica, Portugal 3 Institute of Bioorganic Chemistry, National Academy of Sciences Minsk, Belarus
This corrigendum report describes the study of the comparison of human cytochrome b5 (b5) with rat b5 when coupled with human cytochrome P450 CYP1A2, 2A6 or 2E1. Results indicate a role of the N-terminal part of b5 in the coupling with CYP. Indeed, the plasmid pLCM-b5-RED used in our former study on b5 [Duarte et al. (2005) Mutagenesis, 20(2), 193–100] erroneously contained rat b5. Plasmid pLCM-b5-RED was corrected with human b5 and subsequently all experimental work was repeated as was described for the rat b5 plasmid. Although absolute values of contents and activities were lower, all key-findings as found for rat b5 could be confirmed using human b5. The physiological relevant co-expression of the members of the cytochrome P450 complex, CYP, NADPH-cytochrome P450 oxidoreductase (RED) and human b5 could be demonstrated in the different BTC strains, as was found before. The stimulatory effect of human b5 on the activity of CYP1A2, CYP2A6 and CYP2E1 was in general similar, when compared with rat b5, though less quantitatively pronounced. This was both the case when using membrane preparations as well as by the bioactivation of procarcinogens using the bacterial mutagenicity assay. Human b5 stimulated the bioactivation of all compounds as described for rat b5, except for CYP1A2 mediated bioactivation of 2-aminoanthracene (2AA), which was not stimulated by human b5. All other main findings of the effect of rat b5 were confirmed with human b5, i.e. for CYP2A6: N-nitrosodiethylamine (NNdEA): 
14-fold increase (23-fold with rat b5) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK): 3-fold (9-fold with rat b5); for CYP2E1: NNdEA: 1.5-fold increase (3-fold with rat b5); NNK: no mutagenicity with or without human b5. Both CYP2A6 and CYP2E1 demonstrated total dependence on the presence of human b5 for N-nitrosodi-n-propylamine (NNdPA) mutagenicity, as was shown before with rat b5.
*To whom correspondence should be addressed. Tel: +351213610297; Fax: +351213622018; Email: mkranendonk.gene{at}fcm.unl.pt