Cytochrome P450-Dependent Mixed Function Oxidases (MFO) System Dynamics During the Poly Aromatic Hydrocarbon (PAH) Metabolism in Green Mussel Perna Viridis (Linnaeus, 1758)

Abstract

Polyaromatic hydrocarbons (PAH's) are the prominent and most common pollutants in aquatic environments, particularly in marine water. The discharge of hydrocarbons into the sea might be of great concern for marine species living close to dumping sites. Therefore, toxicological properties of hydrocarbons released into marine environments need to be evaluated. PAH pollution potential may be predicted by assessing the induction of hepatic cytochrome P450-associated enzyme activity. The inducibility and activity of phase I reduction nicotinamide adenine dinucleotide phosphate, reduced (NADPH) cytochrome c reductase (CCR), cytochrome c oxidase (COX) and three CYP450 isoforms (benzyloxyresorufin - O-dealkylase [BROD], ethoxyresorufin-O-dealkylase [EROD] and methoxyresorufin-O-dealkylase [MROD] ) enzymes were measured in the hepatic S9 fraction prepared from Perna viridis collected from three sites: a highly oil-polluted site (Kasimedu fishing harbor, Rayapuram, Chennai [Station1]); a moderately polluted off-shore site, about 3 Km away from this area [Station 2]; and the least oil-polluted site (Vellar estuary, Parangipettai [Station 3], which was a reference site.) The levels of BROD (CYP2B6), MROD (CYP1A2) and EROD (CYP1A1) in the tissues of green mussel were measured using Spectro-Fluorometer SL-174, (ELICO, India). All the MFO enzymes exhibited a hierarchical dose-dependent activity in response to oil pollution in these study areas. Samples from the heavily oil-polluted (Kasimedu Station-1 and Station-2) areas exhibited greater activity of all enzymes than the least oil-polluted (Vellar estuary) reference area. Among the enzymes analyzed, the MROD activity was best correlated with the level of hydrocarbon contamination (P < 0.05). Therefore MROD can be considered as a robust biomarker for petroleum hydrocarbons in P. viridis.

Keywords:

• cytochrome P450
• cytochrome c reductase
• cytochrome c oxidase
• alkyloxyresorufin-O-dealkylases
• polyaromatic hydrocarbon
• biotransformation

The authors wish to record their thanks to the Ministry of Earth Sciences, Govt of India for financial support, and to the Department of Science & Technology Fund for Improvement of S & T Infrastructure in Higher Educational Instutions and University Grants Commission-Special Assistance Programme for Instrumental facilities.