Metabolic fate of aromatic amines in the mussel Mytilus galloprovincialis

Abstract

The postmitochondrial fraction of the digestive gland from the marine mussel Mytilus galloprovincialis possesses FAD-containing monooxygenase (EC 1.14.38) but lacks cytochrome P-450 dependent benzo(a)pyrene monooxygenase (EC 11.4.14.1). This is also evidenced by the ability of the mussel preparation to activate carcinogenic aromatic amines, but not carcinogenic benzo(a)pyrene, to Salmonella typhimurium TA 98 mutagens. This metabolic activity is NADPH dependent. Mussel digestive gland postmitochondrial fraction also possesses the enzymes needed for the detoxicating part of the aromatic amine metabolism: UDP-glucuronyl transferase (EC 2.4.1.17) and β-glucuronidase (EC 3.2.1.31). Under the experimental conditions used here, this aromatic amine metabolic pathway converts up to 8% of 2-acetylamino(9-14C)fluorene, but not (G-3H)benzo(a)pyrene, to water soluble glucuronides. Glucuronic acid stimulates the formation of these glucuronides. The metabolites liberated from these glucuronides by the β-glucuronidase treatment could be converted to TA 98 strain mutagens by the carp liver postmitochondrial fraction, but not by the mussel's digestive gland preparation. The presence of such a selective potential for the bioactivation and detoxication of aromatic amines, and not polycyclic aromatic hydrocarbons, in the marine invertebrate(s) may bring new insight to our understanding of the effects and the fate of carcinogens in the marine environment.