Occurrence of Independent Systems for the Cleavage of Folic Acid and Citrovorum Factor in Rat Liver

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RECENT work has demonstrated that extracts from animal tissues can actively degrade folic acid1,2 and citrovorum factor3 at the C9—N10 linkage with the liberation of a diazotizable amine. Whether the same enzyme systems are involved in the cleavage of the two substrates is, however, not established. The horse-liver fraction which has been shown to degrade citrovorum factor was inactive towards folic acid3. In a recent paper, Dinning et al. 4 have suggested that the transformation of folic acid into a diazotizable amine by slices and homogenates of rat livers takes place with the intermediate formation of citrovorum factor. In the course of studies on folic acid degradation by purified fractions from rat liver, we prepared extracts which degrade folic acid but not citrovorum factor. Furthermore, A-methopterin has been found to inhibit selectively the cleavage of folid acid in acetone-dried powder extracts, but the citrovorum factor remains unaffected.

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    Braganca, B. M., Aravindakshan, I., and Ghanekar, D. S., Biochim. Biophys. Acta, 25, 623 (1957).

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    Keresztesy, J. C., and Silverman, M., J. Amer. Chem. Soc., 75, 1512 (1953).

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    Dinning, J. S., Sime, J. T., Work, P. S., Allen, B., and Day, P. L., Arch. Biochem. Biophys., 66, 114 (1957).

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    Bratton, A. C., and Marshall, E. K., J. Biol. Chem., 128, 537 (1939).

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    Silverman, M., Keresztesy, J. C., Koval, G. J., and Gardiner, R. C., J. Biol. Chem., 226, 83 (1957).

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KENKARE, U., BRAGANCA, B. Occurrence of Independent Systems for the Cleavage of Folic Acid and Citrovorum Factor in Rat Liver. Nature 181, 548–549 (1958) doi:10.1038/181548a0

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