The Experts below are selected from a list of 1467 Experts worldwide ranked by ideXlab platform
Yannick Le Marchand Brustel - One of the best experts on this subject based on the ideXlab platform.
-
regulation of glycogen Phosphorylase and glycogen synthase by adrenalin in soleus muscle of Phosphorylase kinase deficient mice
FEBS Journal, 2005Co-Authors: Patricia T W Cohen, Philip Cohen, Yannick Le Marchand BrustelAbstract:Mixed skeletal muscles of ICR/IAn mice contain 0.2% of the Phosphorylase kinase activity found in C3H/He-mg mice at pH 8.2 in the presence of Ca2+. This lack of activity is caused by the absence of the normal Phosphorylase kinase protein (Cohen, P. T. W. et al. (1976) Eur. J. Biochem. 66, 347–356). The trace residual activity in ICR/IAn mice has quite different properties from the normal enzyme. It has a much higher activity ratio (pH 6.8/8.2), its activity is less dependent on Ca2+ and it is not activated by cyclicAMP-dependent protein kinase or by trypsin. Its elution behaviour on Sepharose 413 also differs from the normal enzyme. A consequence of the higher activity ratio (pH 6.8/8.2) and decreased effect of Ca2+, is that mixed skeletal muscles of ICR/IAn mice contain 7% of normal activity at pH 6.8 in the absence of Ca2+. The activity of Phosphorylase kinase in C3H/He-mg control mice is sixfold lower in red oxidative (soleus) muscle and 15-fold lower in cardiac muscle than in mixed skeletal muscle. In contrast, the trace residual activity in ICR/IAn mice is present at the same level in soleus muscle, cardiac muscle and mixed skeletal muscle. Soleus muscles of ICR/IAn mice therefore contain 1.5% of normal activity at pH 8.2 in the presence of Ca2+ and 30% of normal activity at pH 6.8 in the absence of Ca2+. Cardiac muscle contains 6% of normal activity at pH 8.2 in the presence of Ca2+ and 60% of normal activity at pH 6.8 in the absence of Ca2+. When isolated soleus muscles were incubated with adrenalin, the level of Phosphorylase a in ICR/IAn mice rose from 2.8% in the absence to 5.7% in the presence of the hormone. In contrast, the level of Phosphorylase a in normal mice varied from 2.4% to 11.1% in the absence of adrenalin, and increased to 17.7–23.9% in the presence of the hormone. It is concluded that the trace Phosphorylase kinase activity in ICR/IAn mice is capable of phosphorylating Phosphorylase b in vivo and that this enzyme is responsible for the very low level of Phosphorylase a in resting soleus muscle of ICR/IAn mice, and perhaps even in normal mice. Since the residual enzyme cannot be activated by cyclic-AMP-dependent protein kinase, the elevation of Phosphorylase a by adrenalin may be caused by an inhibition of Phosphorylase Phosphatase. The possibility that this occurs through the activation of protein Phosphatase inhibitor 1 by cyclic-AMP-dependent protein kinase is discussed. Incubation of soleus muscles with adrenalin decreased the activity ratio (+ glucose 6-phosphate) of glycogen synthase from 0.24 to 0.08 in ICR/IAn mice and 0.31 to 0.14 in C3H/He-mg or Swiss albino mice. These results demonstrate that the inactivation of glycogen synthase by adrenalin in resting soleus muscle does not result from the activation of Phosphorylase kinase by cyclic-AMP-dependent protein kinase. It is most likely mediated by a direct phosphorylation catalysed by cyclic-AMP-dependent protein kinase, although the activation of protein Phosphatase inhibitor 1 may also contribute to the effect.
Shigeru Tsuiki - One of the best experts on this subject based on the ideXlab platform.
-
purification and subunit structure of rat liver phosphoprotein Phosphatase whose molecular weight is 260000 by gel filtration Phosphatase ib
FEBS Journal, 2005Co-Authors: Shinri Tamura, Shigeru TsuikiAbstract:1 Phosphoprotein Phosphatase IB is a form of rat liver phosphoprotein Phosphatase, distinguished from the previously studied phosphoprotein Phosphatase II [Tamara et al. (1980) Eur. J. Biochem. 104, 347–355] by earlier elution from DEAE-cellulose, by higher molecular weight on gel filtration (260000) and by lower activity toward Phosphorylase a. This enzyme was purified to apparent homogeneity by chromatography on DEAE-cellulose, aminohexyl—Sepharose-4B, histone-Sepharose-4B, protamine-Sepharose-4B and Sephadex G-200. 2 The molecular weight of purified Phosphatase IB was 260000 by gel filtration and 185000 from s 20° C, and Stokes' radius. Using historic Phosphatase activity as the reference for comparison, the Phosphorylase Phosphatase activity of purified Phosphatase IB was only one-fifth that of Phosphatase II. 3 Sodium dodecyl sulfate gel electrophoresis revealed that Phosphatase IB contains three types of subunit, namely α, β and γ, whose molecular weights are 35000, 69000 and 58000, respectively. The α subunit is identical to the α subunit α Phosphatase II. While the β subunit is also identical or similar to the β subunit of Phosphatase II, the γ subunit appears to be unique to Phosphatase IB. 4 When purified Phosphatase IB was treated with 2-mercaptoethanol at –20° C, the enzyme was dissociated to release the catalytically active α subunit. Along with this dissociation, there was a 7.4-fold increase in Phosphorylase Phosphatase activity; but historic Phosphatase activity increased only 1.6-fold. The possible functions of the γ subunit are discussed in relation to this activation of enzyme.
Loranne Agius - One of the best experts on this subject based on the ideXlab platform.
-
Role of glycogen Phosphorylase in liver glycogen metabolism
Molecular Aspects of Medicine, 2015Co-Authors: Loranne AgiusAbstract:Liver glycogen is synthesized after a meal in response to an increase in blood glucose concentration in the portal vein and endocrine and neuroendocrine signals, and is degraded to glucose between meals to maintain blood glucose homeostasis. Glycogen degradation and synthesis during the diurnal cycle are mediated by changes in the activities of Phosphorylase and glycogen synthase. Phosphorylase is regulated by phosphorylation of serine-14. Only the phosphorylated form of liver Phosphorylase (GPa) is catalytically active. Interconversion between GPa and GPb (unphosphorylated) is dependent on the activities of Phosphorylase kinase and of Phosphorylase Phosphatase. The latter comprises protein Phosphatase-1 in conjunction with a glycogen-targeting protein (G-subunit) of the PPP1R3 family. At least two of six G-subunits (GL and PTG) expressed in liver are involved in GPa dephosphorylation. GPa to GPb interconversion is dependent on the conformational state of Phosphorylase which can be relaxed (R) or tense (T) depending on the concentrations of allosteric effectors such as glucose, glucose 6-phosphate and adenine nucleotides and on the acetylation state of lysine residues. The G-subunit, GL, encoded by PPP1R3B gene is expressed at high levels in liver and can function as a Phosphorylase Phosphatase and a synthase Phosphatase and has an allosteric binding site for GPa at the C-terminus which inhibits synthase Phosphatase activity. GPa to GPb conversion is a major upstream event in the regulation of glycogen synthesis by glucose, its downstream metabolites and extracellular signals such as insulin and neurotransmitters.
David L. Brautigan - One of the best experts on this subject based on the ideXlab platform.
-
Phosphoprotein inhibitors of protein Phosphatase-1.
Methods in Enzymology, 2003Co-Authors: Craig A. Leach, Nikolaos A Tountas, David L. BrautiganAbstract:Publisher Summary The chapter discusses phosphoprotein inhibitors of protein Phosphatase-1(PP1). Over 25 years ago, a search for proteins that could regulate Phosphorylase Phosphatase yielded heat-stable proteins that were called “inhibitor-1” (I-1) and “inhibitor-2” (I-2). I-1 potency as an inhibitor increased several hundred-fold after phosphorylation of Thr35 by cAMP-dependent protein kinase (PKA), whereas inhibitor-2 was effective without prior phosphorylation. Inhibitor-1 became the prototype for other phosphoprotein inhibitors of PP1. To distinguish protein phosphates in type-1 (PP1, sensitive to inhibitors) from type-2, these inhibitor proteins are made use of subsequently.. Several new PP1 inhibitor phosphoproteins, such as NIPP-1, inhibitor-4, CPI-17, PHI-1 and KEPI have been discovered in mammalian cells. Regulation of PP1 in cells incorporates the various inhibitor phosphoproteins to selectively target a subset of PP1 holoenzymes. This way the inhibitor proteins work in concert with the PP1 regulatory subunits. Study of the phosphorylation of the PP1 inhibitors takes on added significance for understanding signaling processes, and the chapter describes various methods developed for that purpose.
Patricia T W Cohen - One of the best experts on this subject based on the ideXlab platform.
-
regulation of glycogen Phosphorylase and glycogen synthase by adrenalin in soleus muscle of Phosphorylase kinase deficient mice
FEBS Journal, 2005Co-Authors: Patricia T W Cohen, Philip Cohen, Yannick Le Marchand BrustelAbstract:Mixed skeletal muscles of ICR/IAn mice contain 0.2% of the Phosphorylase kinase activity found in C3H/He-mg mice at pH 8.2 in the presence of Ca2+. This lack of activity is caused by the absence of the normal Phosphorylase kinase protein (Cohen, P. T. W. et al. (1976) Eur. J. Biochem. 66, 347–356). The trace residual activity in ICR/IAn mice has quite different properties from the normal enzyme. It has a much higher activity ratio (pH 6.8/8.2), its activity is less dependent on Ca2+ and it is not activated by cyclicAMP-dependent protein kinase or by trypsin. Its elution behaviour on Sepharose 413 also differs from the normal enzyme. A consequence of the higher activity ratio (pH 6.8/8.2) and decreased effect of Ca2+, is that mixed skeletal muscles of ICR/IAn mice contain 7% of normal activity at pH 6.8 in the absence of Ca2+. The activity of Phosphorylase kinase in C3H/He-mg control mice is sixfold lower in red oxidative (soleus) muscle and 15-fold lower in cardiac muscle than in mixed skeletal muscle. In contrast, the trace residual activity in ICR/IAn mice is present at the same level in soleus muscle, cardiac muscle and mixed skeletal muscle. Soleus muscles of ICR/IAn mice therefore contain 1.5% of normal activity at pH 8.2 in the presence of Ca2+ and 30% of normal activity at pH 6.8 in the absence of Ca2+. Cardiac muscle contains 6% of normal activity at pH 8.2 in the presence of Ca2+ and 60% of normal activity at pH 6.8 in the absence of Ca2+. When isolated soleus muscles were incubated with adrenalin, the level of Phosphorylase a in ICR/IAn mice rose from 2.8% in the absence to 5.7% in the presence of the hormone. In contrast, the level of Phosphorylase a in normal mice varied from 2.4% to 11.1% in the absence of adrenalin, and increased to 17.7–23.9% in the presence of the hormone. It is concluded that the trace Phosphorylase kinase activity in ICR/IAn mice is capable of phosphorylating Phosphorylase b in vivo and that this enzyme is responsible for the very low level of Phosphorylase a in resting soleus muscle of ICR/IAn mice, and perhaps even in normal mice. Since the residual enzyme cannot be activated by cyclic-AMP-dependent protein kinase, the elevation of Phosphorylase a by adrenalin may be caused by an inhibition of Phosphorylase Phosphatase. The possibility that this occurs through the activation of protein Phosphatase inhibitor 1 by cyclic-AMP-dependent protein kinase is discussed. Incubation of soleus muscles with adrenalin decreased the activity ratio (+ glucose 6-phosphate) of glycogen synthase from 0.24 to 0.08 in ICR/IAn mice and 0.31 to 0.14 in C3H/He-mg or Swiss albino mice. These results demonstrate that the inactivation of glycogen synthase by adrenalin in resting soleus muscle does not result from the activation of Phosphorylase kinase by cyclic-AMP-dependent protein kinase. It is most likely mediated by a direct phosphorylation catalysed by cyclic-AMP-dependent protein kinase, although the activation of protein Phosphatase inhibitor 1 may also contribute to the effect.