Functional differences in the cytochrome P450 1 family enzymes from Zebrafish (Danio rerio) using heterologously expressed proteins

Abstract

Mammalian cytochrome P4501 (CYP1) genes are well characterized, but in other vertebrates only the functions of CYP1A genes have been well studied. We determined the catalytic activity of zebrafish CYP1A, CYP1B1, CYP1C1, CYP1C2 and CYP1D1 proteins using 11 fluorometric substrates and benzo[a]pyrene (BaP). The resorufin-based substrates, 7-ethoxyresorufin, 7-methoxyresorufin, and 7-benzyloxyresorufin, were well metabolized by all CYP1s except CYP1D1. CYP1A metabolized nearly all substrates tested, although rates for non-resorufin substrates were typically lower than resorufin-based substrates. Zebrafish CYP1s did not metabolize 7-benzyloxyquinoline, 3-[2-(N,N-diethyl-N-methylamino)ethyl]-7-methoxy-4-methylcoumarin or 7-methoxy-4-(aminomethyl)-coumarin. CYP1B1 and CYP1C2 had the highest rates of BaP metabolism. 3-hydroxy-BaP was a prominent metabolite for all but CYP1D1. CYP1A showed broad specificity and had the highest metabolic rates for nearly all substrates. CYP1C1 and CYP1C2 had similar substrate specificity. CYP1D1 had very low activities for all substrates except BaP, and a different regioselectivity for BaP, suggesting that CYP1D1 function may be different from other CYP1s.

Tissue-Specific Metabolism of Benzo[a]pyrene in Rainbow Trout (Oncorhynchus mykiss): A Comparison between the Liver and Immune Organs

“…Organ differences in BaP metabolite patterns might be related to tissue-specific expression of CYPs. Here, we studied only CYP1A, but multiple cytochrome forms participate in BaP metabolism, including CYP1A1, CYP1A2, CYP1B1, and several members of the CYP2 subfamilies and CYP3A4 (Bauer et al, 1995;Gautier et al, 1996;Scornaienchi et al, 2010). The activities of these enzymes can vary between organs and even between specific immune cell types (Okano et al, 1979;Baron et al, 1998;Kapitulnik and Strobel, 1999).…”

Alteration of cytochrome P450 1 regulation and HSP 70 level in brain of juvenile common carp (Cyprinus carpio) after chronic exposure to tributyltin

“…EROD is classically used as a biomarker for CYP1A catalytic activity in mammals, birds, and fish (Whyte et al 2000), although it seems probable that also other CYP450 1 forms may deethylate ethoxyresorufin to some extent (Scornaienchi et al 2010). With the increasing EROD activity, the expression level of CYP1A was markedly induced in our present study.…”

“…However, some other studies showed that a compound shown to inhibit EROD activity also could inhibit other CYP450 forms than CYP1A (Hasselberg et al 2005;Beijer et al 2013). Results from a recent study by Scornaienchi et al (2010) suggest that CYP1A and CYP1C proteins are primarily responsible for the degradation of estradiol in fish. The strong induction of brain EROD activity and the markedly induced CYP1A mRNA expression in fish brain exposed to TBT are therefore noteworthy observations.…”

Effects of chronic exposure to tributyltin on tissue-specific cytochrome P450 1 regulation in juvenile common carp

“…Additional, some other studies showed that a compound shown to inhibit EROD activity also could inhibit other CYP450 forms, besides CYP1A. Results from a recent study by Scornaienchi et al (2010) suggest that CYP1A and CYP1C proteins are primarily responsible for the degradation of estradiol in fish. The induction of CYP1B mRNA in the fish was clear but considerably weaker than the CYP1A induction.…”

“…EROD is classically used as a biomarker for CYP1A catalytic activity in mammals, birds, and fish (Whyte et al, 2000), although it seems probable that also other CYP450 1 forms may deethylate ethoxyresorufin to some extent (Scornaienchi et al, 2010). With the increasing EROD activity, the expression level of CYP1A was markedly induced in all tissues of fish exposed to TBT.…”