MICROSOMAL DRUG HYDROXYLASE-ACTIVITY OF TETRAHYMENA-PYRIFORMIS

1. By spectrophotometric determination the content of cytochrome P450 in the microsomal preparation from Tetrahymena pyriformis (strain WH-14) was estimated to be less than 0.014 nmol/mg protein. Optical absorption spectroscopy at 77°K revealed that the microsomal cytochromes mainly consist of b-type heme protein. 2. The microsomal NADPH-oxidase activity was inhibited by hydroxylase inhibitors such as metyrapone, amphenone B and elipten phosphate to a much lesser extent compared with rat liver microsomal activity. 3. No significant hydroxylation activity of xenobiotics by the protozoan microsomal sample was detected. The activity was not induced by administration of phenobarbital or 3-methylcholanthrene. 4. Nonparasitic protozoon Tetrahymena pyriformis appears to have very low if any cytochrome P450-dependent detoxication mechanism. These observations are in contrast to the observation by Agosin et al., 1976, who reports a weak but detectable activity of drug hydroxylation in parasitic protozoon Trypanosoma cruzi. © 1979.