[Cleavage and synthesis of sialic acids with aldolase. NMR studies of stereochemistry, kinetics, and mechanisms].
1H-NMR spectroscopy was used to study cleavage and synthesis of N-acetyl- and N-glycoloyl-D-neuraminic acid by Clostridium perfringens aldolase. Whereas the alpha-anomers of Neu5Ac and Neu5Gc serve as substrate in the cleavage reaction, alpha-ManNAc and alpha-ManNGc are its primary products. The same alpha-anomers are needed by the aldolase for the synthesis of Neu5Ac and Neu5Gc. During the enzyme reaction in D2O both H-atoms at C-3 of Neu5Ac are exchanged by deuterium, H-3e reacting faster than H-3a. Rate constants and concentrations at equilibrium of reactants are temperature- and pH-dependent: The amount of Neu5Ac in equilibrium increases with decreasing temperature and increasing pH-value. Based on these results a mechanism of aldolase action is discussed.
Baumann
W
W
Organisch-Chemisches Institut der Universität Heidelberg.
Freidenreich
J
J
Weisshaar
G
G
Brossmer
R
R
Friebolin
H
H
D003016:Clostridium perfringens / Q000201:enzymology; D005634:Fructose-Bisphosphate Aldolase; D006868:Hydrolysis; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009439:Neuraminidase; D010446:Peptide Fragments / Q000032:analysis; D012794:Sialic Acids / Q000032:analysis*; D013696:Temperature
D010446:Peptide Fragments; D012794:Sialic Acids; D009439:Neuraminidase; D005634:Fructose-Bisphosphate Aldolase
Spaltung und Synthese von Sialinsäuren mit Aldolase. 1H-NMR-Untersuchungen zur Stereochemie, zur Kinetik und zum Mechanismus.