Phosphorylase kinase (PhK) is a serine/threonine-specific protein kinase which activates glycogen phosphorylase to release glucose-1-phosphate from glycogen. PhK phosphorylates glycogen phosphorylase at two serine residues, triggering a conformational shift which favors the more active glycogen phosphorylase “a” form over the less active glycogen phosphorylase b.[1]
The protein is a hexadecameric holoenzyme—that is, a homotetramer in which each subunit is itself a tetramer—arranged in an approximate “butterfly” shape. Each of the subunits is composed of an α, β, γ and δ subunit. The γ subunit is the site of the enzyme's catalytic activity while the other three subunits serve regulatory functions.
When unmodified, the α and β subunits inhibit the enzyme's catalysis, but phosphorylation of both these subunits by protein kinase A (PKA, or cAMP-dependent protein kinase) reduces their respective inhibitory activities. The δ subunit is the ubiquitous eukaryotic protein calmodulin which itself has 4 calcium ion binding sites. When cytosolic Ca2+ levels rise-to as low as 10−7 M—the δ subunit undergoes a large conformational change that activates the kinase's activity by binding to a complementary hydrophobic patch on the catalytic γ subunit.[2]
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and 18 Related for: Phosphorylase kinase information
Phosphorylasekinase (PhK) is a serine/threonine-specific protein kinase which activates glycogen phosphorylase to release glucose-1-phosphate from glycogen...
cause similar problems. GSD type VIII (GSD 8): In the past, liver phosphorylase-b kinase deficiency was considered a distinct condition, however it has been...
Glycogen phosphorylase is one of the phosphorylase enzymes (EC 2.4.1.1). Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis in animals...
during glycolysis. Kinases are part of the larger family of phosphotransferases. Kinases should not be confused with phosphorylases, which catalyze the...
In biochemistry, phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate+hydrogen) to an acceptor...
protein kinase A (cAMP-dependent protein kinase). This enzyme, in turn, activates phosphorylasekinase, which then phosphorylates glycogen phosphorylase b (PYG...
enzyme phosphorylasekinase. This latter enzyme is itself activated by protein kinase A and deactivated by phosphoprotein phosphatase-1. Protein kinase A itself...
In cell biology, protein kinase A (PKA) is a family of serine-threonine kinase whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA...
by the enzyme glycogen phosphorylase. In the muscles, glycogenolysis begins due to the binding of cAMP to phosphorylasekinase, converting the latter...
Phosphorylase b kinase gamma catalytic chain, testis/liver isoform is an enzyme that in humans is encoded by the PHKG2 gene. The PHKG2 gene provides instructions...
Protein kinase B (PKB), also known as Akt, is the collective name of a set of three serine/threonine-specific protein kinases that play key roles in multiple...
In cell biology, Protein kinase C, commonly abbreviated to PKC (EC 2.7.11.13), is a family of protein kinase enzymes that are involved in controlling...
or CCaMK, is an abbreviation for the Ca2+/calmodulin-dependent protein kinase class of enzymes. CAMKs are activated by increases in the concentration...
which leads to further activation of phosphorylasekinase. Phosphorylasekinase phosphorylates glycogen phosphorylase, which then breaks down glycogen leading...
by glycogen synthase kinase-3, and extension of the N-terminal sequence containing the site phosphorylated by phosphorylasekinase". Eur. J. Biochem. 107...
a kinase that in humans is encoded by the MTOR gene. mTOR is a member of the phosphatidylinositol 3-kinase-related kinase family of protein kinases. mTOR...
Myophosphorylase comes in two forms: form 'a' is phosphorylated by phosphorylasekinase, form 'b' is not phosphorylated. Form 'a' is de-phosphorylated into...
Myophosphorylase (muscle glycogen phosphorylase) comes in two forms: form 'a' is phosphorylated by phosphorylasekinase, form 'b' is not phosphorylated...
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