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EC 2.4.1.186 Details
EC number
2.4.1.186
Accepted name
glycogenin glucosyltransferase
Reaction
UDP-α-D-glucose + glycogenin = UDP + α-D-glucosylglycogenin
Other name(s)
glycogenin, priming glucosyltransferase, UDP-glucose:glycogenin glucosyltransferase
Systematic name
UDP-α-D-glucose:glycogenin α-D-glucosyltransferase
CAS registry number
117590-73-5
Comment
The first reaction of this enzyme is to catalyse its own glucosylation, normally at Tyr-194 of the protein if this group is free. When Tyr-194 is replaced by Thr or Phe, the enzyme’s Mn2+-dependent self-glucosylation activity is lost but its intermolecular transglucosylation ability remains [7]. It continues to glucosylate an existing glucosyl group until a length of about 5–13 residues has been formed. Further lengthening of the glycogen chain is then carried out by EC 2.4.1.11, glycogen (starch) synthase. The enzyme is not highly specific for the donor, using UDP-xylose in addition to UDP-glucose (although not glucosylating or xylosylating a xylosyl group so added). It can also use CDP-glucose and TDP-glucose, but not ADP-glucose or GDP-glucose. Similarly it is not highly specific for the acceptor, using water (i.e. hydrolysing UDP-glucose) among others. Various forms of the enzyme exist, and different forms predominate in different organs. Thus primate liver contains glycogenin-2, of molecular mass 66 kDa, whereas the more widespread form is glycogenin-1, with a molecular mass of 38 kDa.
History
created 1992 (EC 2.4.1.112 created 1984, incorporated 2007)
EC Tree
2.4.1.3 created 1961, deleted 1972
2.4.1.6 created 1961, deleted 1972
2.4.1.42 created 1972, deleted 1984
2.4.1.51 created 1972, deleted 1984
2.4.1.55 created 1972, deleted 1982
2.4.1.59 created 1972, deleted 1984
2.4.1.61 created 1972, deleted 1984
2.4.1.72 created 1972, deleted 1976
2.4.1.75 created 1976, deleted 2005
2.4.1.76 created 1976, deleted 1984
2.4.1.77 created 1976, deleted 1984
2.4.1.84 created 1976, deleted 1984
2.4.1.89 created 1976, deleted 1984
2.4.1.93 created 1976, deleted 2004
2.4.1.98 created 1980, deleted 1984
2.4.1.107 created 1983, deleted 1984
2.4.1.108 created 1983, deleted 1984
2.4.1.124 created 1984, deleted 2002
2.4.1.151 created 1984, deleted 2002
2.4.1.169 created 1989, deleted 2003
2.4.1.200 created 1992, deleted 2004
2.4.1.204 created 1992, deleted 2003
2.4.1.233 created 2004, deleted 2005