Structural features of cytochrome P450 1A associated with the absence of EROD activity in liver of the loricariid catfish Pterygoplichthys sp

• Published in: Gene 2011-12, Vol.489 (2), p.111-118
• Main Authors: Parente, Thiago E.M., Rebelo, Mauro F., da-Silva, Manuela L., Woodin, Bruce R., Goldstone, Jared V., Bisch, Paulo M., Paumgartten, Francisco J.R., Stegeman, John J.
• Format: Article
• Language: English
• Subjects: agonists; Amino acid; Amino Acid Substitution; amino acids; Ancistrus; Animals; Base Sequence; beta-Naphthoflavone - pharmacology; Biotransformation; Callichthyidae; catfish; Catfishes - metabolism; Corydoras; CYP1A; cytochrome P-450; Cytochrome P-450 CYP1A1 - chemistry; Cytochrome P-450 CYP1A1 - genetics; Cytochrome P-450 CYP1A1 - metabolism; Enzyme Induction; enzymes; Ethoxiresorufin; Fish Proteins - chemistry; Fish Proteins - genetics; Fish Proteins - metabolism; heme iron; Hypostomus; liver; Liver - enzymology; Liver - metabolism; liver microsomes; Loricariidae; messenger RNA; Microsomes, Liver - enzymology; Microsomes, Liver - metabolism; Oxazines - pharmacology; phylogeny; Polychlorinated Biphenyls - pharmacology; Pterygoplichthys; Receptors, Aryl Hydrocarbon - agonists; Receptors, Aryl Hydrocarbon - metabolism; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Sequence Alignment; Sequence Analysis, DNA; Sequence Analysis, Protein; Siluriformes; Substrate Specificity
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2011.07.023

The Amazon catfish genus Pterygoplichthys (Loricariidae, Siluriformes) is closely related to the loricariid genus Hypostomus, in which at least two species lack detectable ethoxyresorufin-O-deethylase (EROD) activity, typically catalyzed by cytochrome P450 1 (CYP1) enzymes. Pterygoplichthys sp. liver microsomes also lacked EROD, as well as activity with other substituted resorufins, but aryl hydrocarbon receptor agonists induced hepatic CYP1A mRNA and protein suggesting structural/functional differences in Pterygoplichthys CYP1s from those in other vertebrates. Comparing the sequences of CYP1As of Pterygoplichthys sp. and of two phylogenetically related siluriform species that do catalyze EROD (Ancistrus sp., Loricariidae and Corydoras sp., Callichthyidae) showed that these three proteins share amino acids at 17 positions that are not shared by any fish in a set of 24 other species. Pterygoplichthys and Ancistrus (the loricariids) have an additional 22 amino acid substitutions in common that are not shared by Corydoras or by other fish species. Pterygoplichthys has six exclusive amino acid substitutions. Molecular docking and dynamics simulations indicate that Pterygoplichthys CYP1A has a weak affinity for ER, which binds infrequently in a productive orientation, and in a less stable conformation than in CYP1As of species that catalyze EROD. ER also binds with the carbonyl moiety proximal to the heme iron. Pterygoplichthys CYP1A has amino acid substitutions that reduce the frequency of correctly oriented ER in the AS preventing the detection of EROD activity. The results indicate that loricariid CYP1As may have a peculiar substrate selectivity that differs from CYP1As of most vertebrate. [Display omitted] ► EROD was not detected in Pterygoplichthys liver microsomes ► CYP1A protein and mRNA were induced by treatments with AhR agonists. ► CYP1A coding region exhibits six exclusive amino acids substitutions. ► EROD substrate docked infrequently and in an unusual position at the active site.