Biosynthesis of folic acid compounds in plants VI. The occurrence and properties of the dihydrofolate-synthesizing enzyme in pea seedlings |
| |
Authors: | IKEDA MASAMICHI; IWAI KAZUO |
| |
Institution: | Research Institute for Food Science, Kyoto Unioersity Kyoto, Japan |
| |
Abstract: | An enzyme, which catalyzes the formation of dihydrofolate fromdihydropteroic acid and L-glutamic acid, was found in pea seedlings.The enzyme was purified approximately 25-fold from the crudeextracts of pea seedlings, and its some properties were investigated.Optimum pH for the enzyme activity was found to be 8.8. Pteroicand tetrahydropteroic acids were not active as substrate. Theenzymatic reaction required as cofactors ATP, divalent (Mg2+or Mn2+) and univalent (K+, NH4+ or Rb+) cations. The productwas characterized as dihydrofolic acid by bioautography. MICHAELIS constants for L-glutamic acid, ATP, dihydropteroicacid and Mg2+ were 7.0x104, 9.0x105, 3.5x106and 1.2x103 M, respectively. The MICHAELIS constant forMn2+ was 3.0x104. The enzyme was inhibited by PCMB orsilver nitrate and, to some extent, by L-aspartic acid. Inhibitionby PCMB was completely reversed by addition of 2-mercaptoethanol.Enzyme activity was distributed widely among plants. The importanceof magnesium and potassium ions for enzyme catalysis is discussed.
1For the previous paper, Part V, see Reference (30). (Received March 28, 1970; ) |
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|