1986 Fiscal Year Final Research Report Summary
Alterations and significance of protein phosphatases, in particular of phosphatase IV, under diabetic conditions
| Project/Area Number |
60480140
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Pathological medical chemistry
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
TSUIKI Shigeru Research Institute for Tuberculosis and Cancer, Tohoku University - Professor, 抗酸菌病研究所, 教授 (90006065)
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| Co-Investigator(Kenkyū-buntansha) |
TAMURA Shinri Research Institute for Tuberculosis and Cancer Tohoku University - Research Asso, 抗酸菌病研究所, 助手 (20124604)
KIKUCHI Kunimi Research Institute for Tuberculosis and Cancer Tohoku University - Associate Pro, 抗酸菌病研究所, 助教授 (20006117)
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| Project Period (FY) |
1985 – 1986
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| Keywords | Protein phosphatase / Diabetes / Liver / Skeletal muscle / Glycogen synthase / グリコゲン / ホスホリラーゼ |
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| Research Abstract |
Previous studies indicated that protein phosphatase is a primary locus when diabetic conditions affect the carbohydrate- and lipid-metabolism of tissues. Liver and skeletal muscle, however, contain multiple species of protein phosphatase; and the fact that the dephosphorylation of glycogen synthase is more profoundly affceted than that of phosphorylase by diabetes suggests that only a particular species is tightly controlled by insulin. In rat liver, strong candidates are previously studied cytosolic phosphatase IA and newly discovered phosphatase IV, which is associated with the glycogen particles. Presently, the purification and characterization of phosphatase IV and the substrate specificity of phosphatase IA were studied.
Almost all the synthase phosphatase activity of rat liver particulate fraction is due to phosphatase IV, which, however, is unable to attack phosphorylase a. Its level is decreased by fasting, normalized by refeeding, and affected also by diabetes. After purification to electrophoretic homogeneity, the enzyme was still inhibited by glycogen and phosphorylase a. SDS-PAGE revealed phosphatase IV being monomeric with <M-r> =70K. Phosphatase IA, on the other hand, was first discovered as acting to liver synthase D preferentially. The enzyme was now found to be incapable of activating skeletal muscle synthase D. This suggests that phosphatase IA may be related to differentiated liver functions.
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Research Products
(11 results)
