ID 2.4.1.186 DE glycogenin glucosyltransferase. AN glycogenin. AN priming glucosyltransferase. CA (1) L-tyrosyl-[glycogenin] + UDP-alpha-D-glucose = alpha-D-glucosyl-L- CA tyrosyl-[glycogenin] + H(+) + UDP. CA (2) [1,4-alpha-D-glucosyl](n)-L-tyrosyl-[glycogenin] + UDP-alpha-D- CA glucose = [1,4-alpha-D-glucosyl](n+1)-L-tyrosyl-[glycogenin] + H(+) + CA UDP. CC -!- The first reaction of this enzyme is to catalyze its own CC glucosylation, normally at a specific Tyr of the protein if this CC group is free; when the Tyr is replaced by Thr or Phe, the enzyme's CC self-glucosylation activity is lost but its intermolecular CC transglucosylation ability remains. CC -!- It continues to glucosylate an existing glucosyl group until a length CC of about 5-13 residues has been formed. CC -!- Further lengthening of the glycogen chain is then carried out by CC EC 2.4.1.11. CC -!- Not highly specific for the donor, using UDP-xylose in addition to CC UDP-glucose (although not glucosylating or xylosylating a xylosyl CC group so added). CC -!- It can also use CDP-glucose and TDP-glucose, but not ADP-glucose or CC GDP-glucose. CC -!- Similarly it is not highly specific for the acceptor, using water CC (i.e. hydrolyzing UDP-glucose) among others. CC -!- Various forms of the enzyme exist, and different forms predominate in CC different organs. CC -!- Thus primate liver contains glycogenin-2, of molecular mass 66 kDa, CC whereas the more widespread form is glycogenin-1, with a molecular CC mass of 38 kDa. CC -!- Formerly EC 2.4.1.112. DR A7A018, GLG1_YEAS7 ; P36143, GLG1_YEAST ; A6ZQJ2, GLG2_YEAS7 ; DR P47011, GLG2_YEAST ; O15488, GLYG2_HUMAN; P46976, GLYG_HUMAN ; DR Q9R062, GLYG_MOUSE ; P13280, GLYG_RABIT ; O08730, GLYG_RAT ; DR H2KYQ5, GYG1_CAEEL ; //