Abstract
3-Phosphoglycerate phosphatase and phosphoglycolate phosphatase were found in leaves of all 52 plants examined. Activities of both phosphatases varied widely between 1 to 20 micromoles per minute per milligram chlorophyll. Plants were grouped into two categories based upon the relative ratio of activity of 3-phosphoglycerate phosphatase to phosphoglycolate phosphatase. This ratio varied between 2:1 to 4:1 in the C(4)-plants except corn leaves which had a low level of 3-phosphoglycerate phosphatase. This ratio was reversed and varied between 1:2 to 1:6 in all C(3)-plants except one bean variety which had large amounts of both phosphatases. By differential grinding procedures for C(4) plants a major part of the 3-phosphoglycerate phosphatase was found in the mesophyll cells and P-glycolate phosphatase in the bundle sheath cells. Phosphoglycolate phosphatase, but not 3-phosphoglycerate phosphatase, was located in chloroplasts of C(3)- and C(4)- plants. Formation of 3-phosphoglycerate phosphatase increased 4- to 12-fold during greening of etiolated sugarcane leaves. This cytosol phosphatase displayed a diurnal variation in sugarcane leaves by increasing 50% during late daylight hours and early evening. It is proposed that the soluble form of 3-phosphoglycerate phosphatase is necessary for carbon transport between the bundle sheath and mesophyll cells during photosynthesis by C(4)-plants. In C(3)- and C(4)-plants this phosphatase initiates the conversion of 3-phosphoglycerate to serine which is an alternate metabolic pathway to glycolate metabolism and photorespiration.