Abstract
The hydrolysis of the donor substrate uridine diphosphate galactose (UDP-Gal) by human blood group B galactosyltransferase (GTB) has been followed by nuclear magnetic resonance in the presence and in the absence of an acceptor substrate analog. It is observed that the presence of the acceptor substrate analog promotes hydrolysis of UDP-Gal. Subsequent analysis of the kinetics of the enzymatic hydrolysis suggests that this effect is due to an increased affinity of GTB for UDP-Gal in the presence of the acceptor analog. Isothermal titration calorimetry experiments substantiate this conclusion. As hydrolysis may be understood as a glycosyl transfer reaction where water serves as universal acceptor, we suggest that in general the binding of acceptor substrates to retaining glycosyltransferases modulates the rate of glycosyl transfer. In fact, this may point to a general mechanism used by retaining glycosyltransferases to discriminate acceptor substrates under physiological conditions.
| Original language | English |
|---|---|
| Article number | cwq019 |
| Journal | Glycobiology |
| Volume | 20 |
| Issue number | 6 |
| Pages (from-to) | 718-723 |
| Number of pages | 6 |
| ISSN | 0959-6658 |
| DOIs | |
| Publication status | Published - 12.02.2010 |
Funding
The authors thank the University of Lübeck for financial support. The DFG and the state of Schleswig-Holstein are thanked for a grant for the cryogenic probe (HBFG 101/192-1). N.S. thanks the Studienstiftung des Deutschen Volkes for a stipend. F.J.M. thanks the Spanish Ministerio de Educación y Ciencia for the FPU predoctoral fellowship (AP2003-4820) and Prof. M. J. Hernaiz (Madrid) for generous support. We thank W. Hellebrandt and T. Köhli for technical assistance.
Research Areas and Centers
- Academic Focus: Center for Infection and Inflammation Research (ZIEL)
