Immunological characterization of flavin-containing monooxygenases from the liver of rainbow trout ( Oncorhynchus mykiss): sexual- and age-dependent differences and the effect of trimethylamine on enzyme regulation

Abstract

Polyclonal antibodies raised against flavin-containing monooxygenase (FMO) enzymes purified from pig liver and rabbit lung were used in conjunction with N, N-dimethylaniline (DMA) N-oxidase to better characterize FMO from the liver of rainbow trout ( Oncorhynchus mykiss). Two proteins reacted with polyclonal antibodies raised against pig liver FMO (PL-1 and PL-2) and anti-rabbit lung FMO (RL-1 and RL-2). Although there was no difference in DMA N-oxidase observed between sexually mature male and female trout liver microsomes, RL-2 and PL-2 were significantly less than RL-1 and PL-1, respectively, in sexually mature females. FMO activity and protein content increased as fish aged. DMA oxidase and FMO isozymes were unaltered after pretreatment with the endogenous substrate trimethylamine. Since antibodies to the purified mammalian enzymes react with proteins of similar MW in trout, some forms of FMO appear to be structurally conserved through evolution.