Resolution of rat liver 10-formyltetrahydrofolate dehydrogenase/hydrolase activities. 1988

G L Case, and P J Kaisaki, and R D Steele
Department of Nutritional Sciences, University of Wisconsin, Madison 53706.

10-Formyltetrahydrofolate dehydrogenase (EC 1.5.1.6) catalyzes the NADP-dependent conversion of 10-formyltetrahydrofolate to tetrahydrofolate and CO2. Previous studies of 10-formyltetrahydrofolate dehydrogenase purified from rat or pig liver homogenized in phosphate buffers indicated the presence of copurifying 10-formyltetrahydrofolate hydrolase activity, which catalyzes conversion of 10-formyltetrahydrofolate to tetrahydrofolate and formate. We find that the supernatant from rat liver homogenized in mannitol/sucrose/EDTA medium contains essentially all of the total cellular 10-formyltetrahydrofolate dehydrogenase activity, but no measurable hydrolase activity. Treating mannitol/sucrose/EDTA-washed mitochondria with Triton X-100 (0.5%) releases hydrolase activity in soluble form. 10-Formyltetrahydrofolate dehydrogenase purified from the mannitol/sucrose/EDTA supernatant has no 10-formyltetrahydrofolate hydrolase activity. Results of kinetic experiments using the hydrolase-free dehydrogenase give a complex rate equation with respect to (6R,S)-10-formyltetrahydrofolate. Double-reciprocal plots fit a 2/1 hyperbolic function with apparent Km values of 3.9 and 68 microM. Our results indicate that 10-formyltetrahydrofolate hydrolase and dehydrogenase are not alternate catalytic activities of a single protein, but represent two closely related and separately compartmentalized hepatic enzymes.

UI MeSH Term Description Entries
D007202 Indicators and Reagents Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499) Indicator,Reagent,Reagents,Indicators,Reagents and Indicators
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D002852 Chromatography, Ion Exchange Separation technique in which the stationary phase consists of ion exchange resins. The resins contain loosely held small ions that easily exchange places with other small ions of like charge present in solutions washed over the resins. Chromatography, Ion-Exchange,Ion-Exchange Chromatography,Chromatographies, Ion Exchange,Chromatographies, Ion-Exchange,Ion Exchange Chromatographies,Ion Exchange Chromatography,Ion-Exchange Chromatographies
D000581 Amidohydrolases Any member of the class of enzymes that catalyze the cleavage of amide bonds and result in the addition of water to the resulting molecules. Amidases,Amidohydrolase
D000587 Oxidoreductases Acting on CH-NH Group Donors Enzymes catalyzing the dehydrogenation of secondary amines, introducing a C Secondary Amine Oxidoreductases,Amine Oxidoreductases, Secondary Amine,Amine Oxidoreductases, Secondary,Oxidoreductases Acting on CH NH Group Donors,Oxidoreductases, Secondary Amine
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus

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