Binding of an acceptor substrate analog enhances the enzymatic activity of human blood group B galactosyltransferase. 2010

Nora Sindhuwinata, and Eva Munoz, and Francisco Javier Munoz, and Monica M Palcic, and Hannelore Peters, and Thomas Peters
Institute of Chemistry, University of Luebeck, Ratzeburger Allee 160, 23538 Luebeck Germany.

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.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D009682 Magnetic Resonance Spectroscopy Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING). In Vivo NMR Spectroscopy,MR Spectroscopy,Magnetic Resonance,NMR Spectroscopy,NMR Spectroscopy, In Vivo,Nuclear Magnetic Resonance,Spectroscopy, Magnetic Resonance,Spectroscopy, NMR,Spectroscopy, Nuclear Magnetic Resonance,Magnetic Resonance Spectroscopies,Magnetic Resonance, Nuclear,NMR Spectroscopies,Resonance Spectroscopy, Magnetic,Resonance, Magnetic,Resonance, Nuclear Magnetic,Spectroscopies, NMR,Spectroscopy, MR
D002151 Calorimetry The measurement of the quantity of heat involved in various processes, such as chemical reactions, changes of state, and formations of solutions, or in the determination of the heat capacities of substances. The fundamental unit of measurement is the joule or the calorie (4.184 joules). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
D004789 Enzyme Activation Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme. Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D005700 Galactosyltransferases Enzymes that catalyze the transfer of galactose from a nucleoside diphosphate galactose to an acceptor molecule which is frequently another carbohydrate. EC 2.4.1.-. Galactosyltransferase
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006868 Hydrolysis The process of cleaving a chemical compound by the addition of a molecule of water.
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013379 Substrate Specificity A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts. Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D014531 Uridine Diphosphate Galactose A nucleoside diphosphate sugar which can be epimerized into UDPglucose for entry into the mainstream of carbohydrate metabolism. Serves as a source of galactose in the synthesis of lipopolysaccharides, cerebrosides, and lactose. UDP Galactose,UDPGal,Uridine Diphosphogalactose,Uridine Pyrophosphogalactose,Diphosphate Galactose, Uridine,Diphosphogalactose, Uridine,Galactose, UDP,Galactose, Uridine Diphosphate,Pyrophosphogalactose, Uridine

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