7 research outputs found
Quantitative Analysis in Nanoliter Wells by Prefilling of Wells Using Electrospray Deposition Followed by Sample Introduction with a Coverslip Method
Remodeling of the Carbohydrate Chains of hCG by Use of Sialyltransferases: Effects on the Biological Activity
Human chorionic gonadotropin (hCG) is a glycoprotein hormone which contains both N- and O-linked
carbohydrate chains. It consists of two subunits, a and 8. The a-subunit contains two N-linked
carbohydrate chains: a mono-antenna and a non-fucosylated bi-antenna. The $-subunit contains both
(two) N and (four) O-linked carbohydrate structures. Both of the N-linked carbohydrate chainsare biantennary,
one of which is fucosylated
Miniaturized Electrospraying as a Technique for the Production of Microarrays of Reproducible Micrometer-Sized Protein Spots
SIALYLTRANSFERASES; THEIR SPECIFICITY AND THEIR USE IN CARBOHYDRATE REMODELLING.
In order to apply sialyltransferases in the remodelling of the
carbohydrate chains on biologically active glycoproteins, it is a
prerequisite to know the fine specificity of these enzymes. In this
report the specificity of several sialyltransferses involved in the
sialylation of O- and N-linked oligosaccharide chains is reviewed.
Also novel results on the branch specificity of a3- and a6-sialyltransferase
are reported.
The potential application of these enzymes in carbohydrate
remodelling was studied using human chorionic gonadotropin (hCG) as a
model glycoprotein. Differently sialylated preparations of this
hormone were obtained and tested for their stimulatory effect on
steroidogenesis in Leydig cells in vitro. Asialo-hCcG appeared to be
only 45% as effective as native hCG. a3-Resialylation of the O-linked
chains on the ß-subunit of this hormone did not restore the
biological activity to a higher level. By contrast, 55% a6-
resialylation of the N-linked chains yielded a preparation which was
almost as active as native hCG. Interestingly, further sialylation by
the a6-sialyltransferase resulted in a decrease of the bio-activity
to levels lower than obtained with asialo-hcG.
It is concluded that the lectin-carbohydrate binding, which is
part of the process that triggers the biological respons of the
target cell can be mimicked by N-linked chains carrying a6-linked
sialic acid. However, too high a density of such residues interferes
with this interaction