Biosynthesis of folic acid compounds in plants VI. The occurrence and properties of the dihydrofolate-synthesizing enzyme in pea seedlings

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概要

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• An enzyme, which catalyzes the formation of dihydrofolate from dihydropteroic acid and L-glutamic acid, was found in pea seedlings. The enzyme was purified ap-proximately 25-fold from the crude extracts of pea seedlings, and its some properties were investigated. Optimum pH for the enzyme activity was found to be 8.8. Pteroic and tetrahydropteroic acids were not active as substrate. The enzymatic reaction required as cofactors ATP, divalent (Mg^<2+> or Mn^<2+>) and univalent (K^+, NH4^+ or Rb^+) cations. The product was characterized as dihydrofolic acid by bioautography. MICHAELIS constants for L-glutamic acid, ATP, dihydropteroic acid and Mg^<2+> were 7.0×10^<-4>, 9.0×10^<-5>, 3.5×10^<-6> and 1.2×10^<-3>M. respectively. The MICHAELIS constant for Mn^<2+> was 3.0×10^<-4>M. The enzyme was inhibited by PCMB or silver nitrate and, to some extent, by L-aspartic acid. Inhibition by PCMB was completely reversed by addition of 2-mercaptoethanol. Enzyme activity was distributed widely among plants. The importance of magnesium and potassium ions for enzyme catalysis is discussed.

• 日本植物生理学会の論文

著者

• Ikeda Masamichi

  Research Institute For Food Science Kyoto University

• IWAI KAZUO

  Research Institute for Food Science, Kyoto University

• Iwai Kazuo

  Research Institute For Food Science Kyoto University

関連論文

• Biosynthesis of folic acid compounds in plants VI. The occurrence and properties of the dihydrofolate-synthesizing enzyme in pea seedlings
• THE DISTRIBUTION OF FROMYLTETRAHYDROFOLATE SYNTHETASE IN PLANTS, AND THE PURIFICATION AND PROPERTIES OF THE ENZYME FROM PEA SEEDLINGS
• The occurrence and properties of methenyltetrahydrofolate cyclohydrolase in plants
• The occurrence and properties of dihydrofolate reductase in pea seedlings

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