P-Chloro-N-methylaniline demethylation by rat kidney subcellular fractions

Subcellular fractions prepared from kidney homogenates catalyzed the demethylation of p-chloro-N-methylaniline (PCMA). The activity of the renal preparations were forty-one percent of the liver 9,000 xg supernatant fraction activity. A differential susceptibility to the addition of carbon monoxide, p-chloromercuribenzoate or the omission of NADPH and magnesium characterized the two preparations. Comparison of the Lineweaver-Burk plots of the PCMA demthylation activities indicated that the maximal velocities and the apparent Michaelis constants (Km) of the two preparations differed. The apparent Km of the renal enzyme was approximately two fold greater than that of the liver. The PCMA demethylation activity of renal preparations is distributed between the cytosol and microsomal subcellular fractions. The results suggest the presence of tissue-related differences between renal and hepatic enzymes which catalyze the demethylation of PCMA.