Phosphorylation of inhibitor-2 and activation of MgATP-dependent protein phosphatase by rat skeletal muscle glycogen synthase kinase
Rat skeletal muscle contains a glycogen synthase kinase (GSK-M) which is not stimulated by Ca/sup 2 +/ or cAMP. This kinase has an apparent Mr of 62,000 and uses ATP but not GTP as a phosphoryl donor. GSK-M phosphorylated glycogen synthase at sites 2 and 3. It phosphorylated ATP-citrate lyase and activated MgATP-dependent phosphatase in the presence of ATP but not GTP. As expected, the kinase also phosphorylated phosphatase inhibitor 2 (I-2). Phosphatase incorporation reached approximately 0.3 mol/mol of I-2. Phosphopeptide maps were obtained by digesting /sup 32/P-labeled I-2 with trypsin and separating the peptides by reversed phase HPLC. Two partially separated /sup 32/P-labeled peaks were obtained when I-2 was phosphorylated with either GSK-M or glycogen synthase kinase 3 (GSK-3) and these peptides were different from those obtained when I-2 was phosphorylated with the catalytic subunit of cAMP-dependent protein kinase (CSU) or casein kinase II (CK-II). When I-2 was phosphorylated with GSK-M or GSK-3 and cleaved by CNBr, a single radioactive peak was obtained. Phosphoamino acid analysis showed that I-2 was phosphorylated by GSK-M or GSK-3 predominately in Thr whereas CSU and CK-II phosphorylated I-2 exclusively in Ser. These results indicate that GSK-M is similar to GSK-3 and to ATP-citrate lyase kinase. However, it appears to differ in Mr from ATP-citrate lyase kinase and it differs from GSK-3 in that it phosphorylates glycogen synthase at site 2 and it does not use GTP as a phosphoryl donor.
- Research Organization:
- Medical College of Ohio, Toledo
- OSTI ID:
- 7119682
- Report Number(s):
- CONF-8606151-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ANIMALS
ATP
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CARBOHYDRATES
CHEMICAL REACTIONS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
ENZYME INHIBITORS
ENZYMES
ESTERASES
GLYCOGEN
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LIQUID COLUMN CHROMATOGRAPHY
MAMMALS
MUSCLES
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PEPTIDE HYDROLASES
PHOSPHATASES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
POLYSACCHARIDES
RADIOISOTOPES
RATS
REACTION KINETICS
RODENTS
SACCHARIDES
SEPARATION PROCESSES
SERINE PROTEINASES
TRACER TECHNIQUES
TRANSFERASES
TRYPSIN
VERTEBRATES