IUBMB Enzyme Nomenclature


Accepted name: glycogen phosphorylase

Reaction: [(1→4)-α-D-glucosyl]n + phosphate = [(1→4)-α-D-glucosyl]n-1 + α-D-glucose 1-phosphate

For diagram of reaction click here.

Other name(s): muscle phosphorylase a and b; amylophosphorylase; polyphosphorylase; amylopectin phosphorylase; glucan phosphorylase; α-glucan phosphorylase; 1,4-α-glucan phosphorylase; glucosan phosphorylase; granulose phosphorylase; maltodextrin phosphorylase; muscle phosphorylase; myophosphorylase; potato phosphorylase; starch phosphorylase; 1,4-α-D-glucan:phosphate α-D-glucosyltransferase; phosphorylase (ambiguous)

Systematic name: (1→4)-α-D-glucan:phosphate α-D-glucosyltransferase

Comments: This entry covers several enzymes from different sources that act in vivo on different forms of (1→4)-α-D-glucans. Some of these enzymes catalyse the first step in the degradation of large branched glycan polymers - the phosphorolytic cleavage of α-1,4-glucosidic bonds from the non-reducing ends of linear poly(1→4)-α-D-glucosyl chains within the polymers. The enzyme stops when it reaches the fourth residue away from an α-1,6 branching point, leaving a highly branched core known as a limit dextrin. The accepted name of the enzyme should be modified for each specific instance by substituting "glycogen" with the name of the natural substrate, e.g. maltodextrin phosphorylase, starch phosphorylase, etc.

Links to other databases: BRENDA, EXPASY, KEGG, PDB, Metacyc, CAS registry number: 9035-74-9


1. Hanes, C.S. The breakdown and synthesis of starch by an enzyme from pea seeds. Proc. R. Soc. Lond. B Biol. Sci. 128 (1940) 421-450.

2. Green, A.A. and Cori, G.T. Crystalline muscle phosphorylase. I. Preparation, properties, and molecular weight. J. Biol. Chem. 151 (1943) 21-29.

3. Baum, H. and Gilbert, G.A. A simple method for the preparation of crystalline potato phosphorylase and Q-enzyme. Nature 171 (1953) 983-984. [PMID: 13063502]

4. Cowgill, R.W. Lobster muscle phosphorylase: purfication and properties. J. Biol. Chem. 234 (1959) 3146-3153. [PMID: 13812491]

5. Chen, G.S. and Segel, I.H. Purification and properties of glycogen phosphorylase from Escherichia coli. Arch. Biochem. Biophys. 127 (1968) 175-186. [PMID: 4878695]

6. Fischer, E.H., Pocker, A. and Saari, J.C. The structure, function and control of glycogen phosphorylase. In: Campbell, P.N. and Greville, G.D. (Eds), Essays in Biochemistry, vol. 6, Academic Press, London and New York, 1970, pp. 23-68.

[EC created 1961, modified 2013]

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