Flavin-containing monooxygenase and ascorbic acid deficiency. Qualitative and quantitative differences.
Ascorbic acid deficiency causes qualitative and quantitative differences in the guinea pig hepatic flavin-containing monooxygenase (FMO). Kinetic studies with purified FMO indicated no significant change in the apparent Km of dimethylaniline or NADPH in ascorbate-supplemented or -deficient animals. Following purification of ascorbate-deficient guinea pig FMO by DEAE-cellulose and blue agarose chromatography, exogenous FAD was required for 15% of the FMO microsomal activity recovered. In contrast, only 5% of the total microsomal enzyme recovered from ascorbate-supplemented animals required exogenous FAD. Furthermore, there was an enhanced sensitivity to time-dependent nonlinearity with the purified ascorbate-deficient guinea pig FMO. The degree of time-dependent nonlinearity was related to the concentration of substrate. Also, purified ascorbate-supplemented guinea pig FMO was stable for 4 weeks at -20 degrees, whereas the ascorbate-deficient enzyme was inactivated. A decrease in the quantity of ascorbate-deficient guinea pig FMO compared to ascorbate-supplemented was indicated by a marked reduction in total FMO activity recovered from blue agarose chromatography and reduced protein staining intensity with SDS-PAGE at 56,000 daltons.
Brodfuehrer
J I
JI
Department of Pharmacology, University of Michigan, Ann Arbor 48109.
Zannoni
V G
VG
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001206:Ascorbic Acid Deficiency / Q000201:enzymology*; D005182:Flavin-Adenine Dinucleotide / Q000494:pharmacology; D006168:Guinea Pigs; D007700:Kinetics; D008970:Molecular Weight; D010105:Oxygenases / Q000032:analysis*
D005182:Flavin-Adenine Dinucleotide; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D001205:Ascorbic Acid