IUBMB Enzyme Nomenclature


Accepted name: 1,4-α-glucan branching enzyme

Reaction: Transfers a segment of a (1→4)-α-D-glucan chain to a primary hydroxy group in a similar glucan chain

Other name(s): branching enzyme; amylo-(1,4→1,6)-transglycosylase; Q-enzyme; α-glucan-branching glycosyltransferase; amylose isomerase; enzymatic branching factor; branching glycosyltransferase; enzyme Q; glucosan transglycosylase; glycogen branching enzyme; plant branching enzyme; α-1,4-glucan:α-1,4-glucan-6-glycosyltransferase; starch branching enzyme; 1,4-α-D-glucan:1,4-α-D-glucan 6-α-D-(1,4-α-D-glucano)-transferase

Systematic name: (1→4)-α-D-glucan:(1→4)-α-D-glucan 6-α-D-[(1→4)-α-D-glucano]-transferase

Comments: Converts amylose into amylopectin. The accepted name requires a qualification depending on the product, glycogen or amylopectin, e.g. glycogen branching enzyme, amylopectin branching enzyme. The latter has frequently been termed Q-enzyme.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9001-97-2


1. Barker, S.A., Bourne, E. and Peat, S. The enzymic synthesis and degradation of starch. Part IV. The purification and storage of the Q-enzyme of the potato. J. Chem. Soc. (Lond.) (1949) 1705-1711.

2. Baum, H. and Gilbert, G.A. A simple method for the preparation of crystalline potato phosphorylase and Q-enzyme. Nature 171 (1953) 983-984.

3. Hehre, E.J. Enzymic synthesis of polysaccharides: a biological type of polymerization. Adv. Enzymol. Relat. Subj. Biochem. 11 (1951) 297-337.

4. Illingworth Brown, B. and Brown, D.H. α-1,4-Glucan:α-1,4-glucan 6-glycosyltransferase from mammalian muscle. Methods Enzymol. 8 (1966) 395-403. [PMID: 16522734]

[EC created 1961]

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