Phosphorylase

<h2 id="function">Function</h2>
<p>Phosphorylases should not be confused with <a href="/facts/Phosphatases/LBJs1fXx">phosphatases</a>, which remove phosphate groups.
In more general terms, phosphorylases are enzymes that catalyze the addition of a phosphate group from an <a href="/facts/Inorganic_phosphate/FDGVCxUG">inorganic phosphate</a> (phosphate + hydrogen) to an acceptor, not to be confused with a <a href="/facts/Phosphatase/LBJs1fXx">phosphatase</a> (a <a href="/facts/Hydrolase/XW89JvNF">hydrolase</a>) or a <a href="/facts/Kinase/dhlHpjnD">kinase</a> (a <a href="/facts/Phosphotransferase/pGqKzt3D">phosphotransferase</a>). A phosphatase removes a phosphate group from a donor using water, whereas a kinase transfers a phosphate group from a donor (usually ATP) to an acceptor.
</p>
<table><tbody><tr><th>Enzyme name</th><th>Enzymes class</th><th>Reaction</th><th>Notes</th></tr><tr><td>Phosphorylase</td><td>Transferase(EC 2.4 and EC 2.7.7)</td><td>A-B + H-OP  ⇌ A-OP + H-B</td><td>transfer group = A = <a href="/facts/Glycosyl/DP5dRJsp">glycosyl</a>- group or <a href="/facts/Nucleotidyl/IE9v9yLF">nucleotidyl</a>- group</td></tr><tr><td>Phosphatase</td><td>Hydrolase(EC 3)</td><td>P-B + H-OH  ⇌ P-OH + H-B</td><td></td></tr><tr><td>Kinase</td><td>Transferase(EC 2.7.1-2.7.4)</td><td>P-B + H-A ⇌ P-A + H-B</td><td>transfer group = P</td></tr><tr><td colspan="4">P = <a href="/facts/Phosphonate/8mg6nNRP">phosphonate</a> group, OP = phosphate group, H-OP or P-OH = inorganic phosphate</td></tr></tbody></table>
<h2 id="types">Types</h2>
<p>The phosphorylases fall into the following categories:
</p>
<ul><li>Glycosyltransferases (EC 2.4)
<ul><li>Enzymes that break down <a href="/facts/Glucan/SGarVY1s">glucans</a> by removing a glucose residue (break <i>O</i>-glycosidic bond)
<ul><li><a href="/facts/Glycogen_phosphorylase/Hhep1hRQ">glycogen phosphorylase</a></li>
<li><a href="/facts/Starch_phosphorylase/F6ejTah1">starch phosphorylase</a></li>
<li><a href="/facts/Maltodextrin_phosphorylase/4rT9rq2p">maltodextrin phosphorylase</a></li></ul></li>
<li>Enzymes that break down <a href="/facts/Nucleoside/G40crf0F">nucleosides</a> into their constituent bases and sugars (break <i>N</i>-glycosidic bond)
<ul><li><a href="/facts/Purine_nucleoside_phosphorylase/5jkKYu9t">Purine nucleoside phosphorylase</a> (PNPase)</li></ul></li></ul></li>
<li>Nucleotidyltransferases (EC 2.7.7)
<ul><li>Enzymes that have phosphorolytic 3' to 5' exoribonuclease activity (break phosphodiester bond)
<ul><li><a href="/facts/RNase_PH/UMQYXUCF">RNase PH</a></li>
<li><a href="/facts/Polynucleotide_Phosphorylase/nLuAPxF8">Polynucleotide Phosphorylase</a> (PNPase)</li></ul></li></ul></li></ul>
<p>All known phosphorylases share catalytic and structural properties.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
</p>
<h2 id="activation">Activation</h2>
<p>Phosphorylase a is the more active R form of glycogen phosphorylase that is derived from the phosphorylation of the less active R form,  phosphorylase b with associated AMP. The inactive T form is either phosphorylated by phosphoylase kinase and inhibited by glucose, or dephosphorylated by phosphoprotein phosphatase with inhibition by ATP and/or glucose 6-phosphate. Phosphorylation requires ATP but dephosphorylation releases free inorganic phosphate ions.
</p>
<h2 id="pathology">Pathology</h2>
<p>Some disorders are related to phosphorylases:
</p>
<ul><li><a href="/facts/Glycogen_storage_disease_type_V/I1vk7MVr">Glycogen storage disease type V</a> - muscle glycogen</li>
<li><a href="/facts/Glycogen_storage_disease_type_VI/vggsXxWP">Glycogen storage disease type VI</a> - liver glycogen</li></ul>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Hydrolase/XW89JvNF">Hydrolase</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="http://mcardlesdisease.org">Muscle phosphorylase deficiency - McArdle's Disease Website</a></li>
<li><a href="https://meshb.nlm.nih.gov/record/ui?name=Phosphorylases">Phosphorylases</a> at the U.S. National Library of Medicine <a href="/facts/Medical_Subject_Headings/C57g2JuF">Medical Subject Headings</a> (MeSH)</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Nelson DL, Lehninger AL, Cox MM (2005). Lehninger Principles of Biochemistry (5th ed.). W. H. Freeman. p. 603. ISBN 978-0-7167-4339-2. <a href="978-0-7167-4339-2" target="_blank">978-0-7167-4339-2</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"PROSITE documentation PDOC00095 [for PROSITE entry PS00102]". PROSITE. <a href="https://prosite.expasy.org/doc/PS00102" target="_blank">https://prosite.expasy.org/doc/PS00102</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
</ol>

Phosphorylase open-in-new

Phosphorylase