Malic enzyme levels are increased by the activation of NADPH‐consuming pathways: detoxification processes

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Abstract
The administration to rats of either t‐butyl hydroperoxide or phénobarbital, compounds that are metabolized through detoxification processes, produces an increase in specific activity of the NADPH‐consuming enzymes, glutathione reductase and NADPH‐cytochrome c reductase. These compounds also produce a very significant increase in the specific activity of malic enzyme. Immunoprecipitation with a specific antibody for malic enzyme indicates that specific activity changes are the result of corresponding changes in the amounts of enzyme protein present. The administration of 1,3‐bis(chloroethyl(‐1‐nitrosourea (a glutathione reductase inhibitor) together with t‐butyl hydroperoxide abolishes any stimulation of malic enzyme activity. These results indicate that an increase in NADPH consumption induces the synthesis of malic enzyme. Alternatively, a protection of enzyme degradation cannot be rigorously excluded.