L. Roden et al., XYLOSYL TRANSFER TO AN ENDOGENOUS RENAL ACCEPTOR - PURIFICATION OF THE TRANSFERASE AND THE ACCEPTOR AND THEIR IDENTIFICATION AS GLYCOGENIN, The Journal of biological chemistry, 269(15), 1994, pp. 11509-11513
A xylosyltransferase in rat kidney, tentatively identified as glycogen
in (Meezan, E., Ananth, S., Manzella, S., Campbell, P., Siegal, S., Pi
llion, D. J., and Roden, L. (1994) J. Biol. Chem. 269,11503-11508), wa
s purified by a procedure in which affinity chromatography on UDP-gluc
uronic acid-agarose was a particularly useful step. The purified mater
ial was nearly homogeneous, as shown by SDS-polyacrylamide gel electro
phoresis and silver staining, and had an electrophoretic mobility corr
esponding to a M(r) of 32,000. The purified enzyme possessed both gluc
osyl- and xylosyltransferase activity, and incubation with UDP-[H-3]xy
lose or UDP-[H-3]glucose yielded a single macromolecular product, whic
h had the same electrophoretic mobility as the major silver-stained co
mponent. These results indicate that the kidney transferase was indeed
glycogenin and that it was functionally analogous to the larger glyco
genin species previously isolated from rabbit muscle. Further examinat
ion of the properties of the rat kidney enzyme showed, i.a., that it w
as inhibited strongly by cytidine 5'-diphosphate. This effect was used
to advantage in an alternative purification procedure, which was appl
ied to beef kidney and involved adsorption of the enzyme to UDP-glucur
onic acid-agarose and subsequent elution with cytidine 5'-diphosphate.
In contrast to glycogenin, glycogen synthase did not catalyze transfe
r from UDP-xylose, and it is suggested that the incorporation of xylos
e into glycogen observed by other investigators was due to glycogenin-
catalyzed xylosyl transfer and subsequent chain elongation by glycogen
synthase.