The occurrence of inorganic pyrophosphate: <scp>d</scp>‐fructose‐6‐phosphate 1‐phosphotransferase in higher plants. I. Initial characterization of partially purified enzyme from <i>Sanseviera trifasciata</i> leaves

Abstract

Among 30 plant species examined, the PPi‐phosphofructokinase (EC 2.7.1.90) was found in leaves of 21 plants. Some of the plants exhibit no activity of ATP‐dependent phosphofructokinase but display only activity of PPi‐phosphofructokinase. A partly purified preparation of PPi‐phosphofructokinase with specific activity of 8.4 Hmol (mg protein) −1 min −1 was obtained from Sanseviera trifasciata leaves. The enzyme is restricted to the cytoplasm, it exhibits pronounced substrate specifity, requires Mg 2+ ions, is inhibited by AMP, PEP, methylenediphosphonate and stabilized by mercaptoethanol. At pH 7.8 with 1.5 m M MgCl 2 the following K M values were observed: pyrophosphate, 0.58 m M ; fructose 6‐phosphate, 0.8 m M . The K M values for substrates of reverse reaction (pH 7.3; 2 m M MgCl 2 ) are of the same order of magnitude: 0.83 m M for fructose 1,6‐diphosphate, and 0.14 m M for orthophosphate. The molecular weight of the studied enzyme is about 125 000 dalton as estimated by gel filtration.