J. Biochem, 1982, Vol. 91, No. 1 177-190
© 1982 Japanese Biochemical Society
research-article |
A Survey of Multiple Phosphoprotein Phosphatases in Cytosols from Rat Tissues and Erythrocytes1
Department of Biochemistry, Hiroshima University School of Medicine Kasumi, Minami-ku, Hiroshima, Hiroshima 734
Phosphoprotein phosphatases [EC 3.1.3.16 [EC] ] acting on P-H2B histone, P-H1 histone, phosphorylase a [EC 2.4.1.1 [EC] ] and glycogen synthase b [ 2.4.1.11 [EC] ] were surveyed in cytosols from various rat tissues and erythrocytes by gel-filtration on Sephadex G-200. A main phosphoprotein phosphatase (Mr=200,000) in tissue cytosols showed preference for phosphorylated histones. In contrast to tissue cytosols, erythrocyte cytosol contained a major phosphoprotein phosphatase (Mr=100,000) which showed strong preference for phosphorylase a and synthase b. Other phos phoprotein phosphatases which preferred phosphorylase a were detected in cytosols from liver, kidney, spleen, and adipose tissue. The molecular weights of the phos phatases were estimated to be 140,000 for liver enzyme and about 90,000 for kidney, spleen, and adipose tissue enzymes. A phosphoprotein phosphatase (Mr=54,000) which preferred synthase b and P-H2B histone was also found in cytosols from various tissues and erythrocytes. This phosphatase was most abundant in liver cytosol and showed strong dependency on Mg2+ and Mn2+. This enzyme was different from other phosphoprotein phosphatases in specificities for different phos phorylated sites on glycogen synthase b. Although treatment with 80% ethanol did not affect the size of liver 54,000 molecular weight enzyme, the same treatment lowered the molecular weights of the major erythrocyte enzyme (Mr=100,000), the main skeletal muscle, liver, and kidney enzymes (Mr=200,000), liver 140,000 molec ular weight enzyme and kidney 93,000 molecular weight enzyme to about 30,000. As a result of this conversion, P-Hi histone phosphatase activities and Mg2+ require ments for P-H2B histone phosphatase activities of these enzymes were greatly sup pressed. Phosphorylase phosphatase activities of the 200,000 and 140,000 molecular weight enzymes were significantly enhanced, but the activity of the 100,000 molecular weight enzyme was essentially unchanged and that of the 93,000 molecular weight
1 This investigation was supported in part by research grants from the Scientific Research Fund of the Ministry of Education, Science and Culture of Japan (1979 to 1980).