Specific Sucrose Phosphatase from Plant Tissues

1. A phosphatase that hydrolyses sucrose phosphate (phosphorylated at the 6-position of fructose) was isolated from sugar-cane stem and carrot roots. With partially purified preparations fructose 6-phosphate, glucose 6-phosphate, fructose 1-phosphate, glucose 1-phosphate and fructose 1,6-diphosphate are hydrolysed at between 0 and 2% of the rate for sucrose phosphate. 2. The activity of the enzyme is increased fourfold by the addition ofMg2+ ions and inhibited by EDTA, fluoride, inorganic phosphate, pyrophosphate, Ca2+ and Mn2+ ions. Sucrose (50nmm) reduces activity by 60%. 3. The enzyme exhibits maximum activity between pH 6-4 and 6-7. The Michaelis constant for sucrose phosphate is between 0-13 and 0-17mM. 4. At least some of the specific phosphatase is associated with particles having the sedimentation properties of mitochondria. 5. A similar phosphatase appears to be present in several other plant species.