Cited by 174Glycogen Storage Diseases and MyoclonusMetabolism, Diabetes, and CancerProtein Kinase Regulation and GTPase Signaling

Phosphorylase kinase: The complexity of its regulation is reflected in the complexity of its structure

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Brushia, Robert, J.·1999·Frontiers in bioscience

Abstract

Intracellular glycogen stores are used to maintain blood-glucose homeostasis during fasting, are a source of energy for muscle contraction, and are used to support a broad range of cellular activities in most tissues. A diversity of signals accelerate glycogen degradation that are mediated by phosphorylase b kinase (Phk), which phosphorylates and thereby activates glycogen phosphorylase. Phk is among the most complex of the protein kinases so far elucidated. It has one catalytic (gamma) subunit and three different regulatory (alpha, beta, and delta) subunits, a molecular mass of 1.3 X 106 daltons, and each holoenzyme molecule is presumed to contain four molecules of each subunit. The three regulatory subunits inhibit the phosphotransferase activity of the gamma subunit. Ca2+ relieves inhibition via the delta subunit, which is identical to calmodulin but remains an integral component of the holoenzyme even when the [Ca2+] is lowered to nanomolar levels. Phosphorylation of the alpha and beta subunits by the 3',5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) also relieves inhibition of the gamma subunit and thereby activates the enzyme. The stimulatory effects of Ca2+ and phosphorylation appear to be structurally coupled and are cooperative. In addition, Phk is activated in vitro by autophosphorylation, limited proteolysis of the regulatory subunits, and various allosteric effectors and these may also be mechanisms of physiological importance. The molecular mechanisms of regulation are currently poorly understood, but new insights are beginning to emerge. This review discusses current knowledge and concepts of the structure, function and regulation of Phk.

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  • Muscular contraction increases cytosolic Ca2+ release and an adrenaline-mediated increase in cAMP, thereby activating phosphorylase kinase and the resultant activation of glycogen phosphorylase.

    “Muscular contraction also increases cytosolic calcium (Ca2+) release and an adrenaline-mediated increase in cyclic AMP (cAMP), thereby activating phosphorylase kinase (PK) and the resultant activation of glycogen phosphorylase [56,57].”

    From Regulation of Energy Substrate Metabolism in Endurance Exercise (2021) · cites this paper as [56]

    The Introduction (page unavailable) describes motor-nerve signals releasing Ca2+ in skeletal muscle, and explains that Ca2+ and cAMP-dependent signaling activate phosphorylase kinase, which in turn activates glycogen phosphorylase. It describes the hormonal and motor-nerve pathways separately; it does not identify adrenaline or say that muscle contraction itself increases cAMP. (LLM, conf=0.85)

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  1. Pickett-Gies C & D. Walsh: Phosphorylase kinase. In: The Enzymes. Academic Press, NY (1986)

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Authors
Brushia, R.
Venue
Frontiers in bioscience
Publisher
IMR Press
Published
1999
Volume
4
Issue
1-3
Pages
d618
ISSN
  • 1093-4715 (ISSN-L)
  • 1093-9946
OpenAlex
W150287726
Cited by
174
References
119
Citations by year
2026: 1 · 2025: 9 · 2024: 6 · 2023: 10 · 2022: 13 · 2021: 6 · 2020: 5 · 2019: 8 · 2018: 8 · 2017: 6 · 2016: 7 · 2015: 3 · 2014: 7 · 2013: 7 · 2012: 6
FWCI
0.64
Type
journal article
Language
en
Open access
Locations
  • Frontiers in bioscience (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Rheumatology › Glycogen Storage Diseases and Myoclonus
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Metabolism, Diabetes, and Cancer
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protein Kinase Regulation and GTPase Signaling
Keywords
phosphorylase kinase, glycogen phosphorylase, enzyme regulation, protein kinase structure, regulatory subunit, calmodulin, calcium signaling, protein kinase A, autophosphorylation, allosteric regulation, glycogenolysis, blood glucose homeostasis
MeSH terms
Amino Acid Sequence, Animals, Calcium, Enzyme Activation, Humans, Hydrogen-Ion Concentration, Isoenzymes, Molecular Sequence Data, Mutation, Phosphorylase Kinase, Phosphorylation, Protein Binding, Structure-Activity Relationship, Substrate Specificity, Consensus Sequence, Protein Structure, Tertiary, Cyclic AMP-Dependent Protein Kinases, Holoenzymes

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