Role of Cytochrome P450 in Xenobiotic Metabolism in Fishes (Review)

Cytochrome P450 (CYP) enzymes encompass a family of heme proteins which plays a prime role in the biotransformation of broad range of exogenous and endogenous substrates. They respond to a wide variety of xenobiotics and therefore detect the presence of both known and unknown pollutants relevant for organisms. Although CYP activity is higher in the fish liver, the enzyme expression is also found in other organs, like the olfactory system, heart, gonads, kidney, gills, placenta, alimentary canal, and brain. CYP genes are highly expressed in the endoplasmic reticulum or mitochondria, particularly of hepatocytes, and least expressed in the brain. Till now, 18 CYP families are identified in fishes, viz., CYP1, CYP2, CYP3, CYP4, CYP5, CYP7, CYP8, CYP11, CYP17, CYP19, CYP20, CYP21, CYP24, CYP26, CYP27, CYP39, CYP46, and CYP51, out of which only 8 families are studied in detail, i.e., CYP1, CYP2, CYP3, CYP4, CYP11, CYP17, CYP19, and CYP26. Several xenobiotics can induce cytochrome P450 monooxygenases altering toxicity of chemical contaminants. The present review paper attempts to present a broad sketch of CYP families in fishes and their classification and functions along with their role in xenobiotic metabolism and pathways.