Glycogenin is the core protein of glycogen proteoglycan and is, at the
same time, a self-glucosylating enzyme which catalyses early glucosyl
transfer steps in the biosynthesis of glycogen, In the course of this
process, glycogenin is glucosylated progressively until an oligosacch
aride containing 8-11 glucose residues has been formed, Although glyco
genin, under physiological conditions, is both enzyme and accepter in
the glucosyl transfer reactions, it is also capable of utilizing p-nit
rophenyl-linked malto-oligosaccharides as exogenous accepters. In view
of the potential usefulness of exogenous accepters in the study of th
e mechanism of the glycogenin reaction, we have expanded the search fo
r such compounds and report here that several alkyl glucosides and alk
yl maltosides may serve as accepters in glucosyl transfer by beef kidn
ey glycogenin. Dodecyl-beta-D-maltoside (K-m similar to 100 mu M) was
the most effective acceptor among the compounds tested and yielded 30
times as much product as p-nitrophenyl-alpha-maltoside. Substantial pr
oduct formation was also observed with tetradecyl-beta-D-maltoside and
octyl-beta-D-maltoside (39 and 22%, respectively, of the value measur
ed for dodecyl-beta-D-maltoside). It was further demonstrated that dod
ecyl-beta-D-maltoside served as an acceptor in the transfer of xylose
from UDP-xylose, indicating that the exogenous substrate behaved simil
arly to glycogenin itself in this regard, Dodecyl-beta-D-maltoside has
already proven useful in the development of a simple glycogenin assay
, and it is further suggested that this and related compounds may be a
ctive in vivo and in cell culture as artificial initiators of glycogen
synthesis.