Friday, April 13, 2018

Discovery of Intermediates of lacZ beta-Galactosidase Catalyzed Hydrolysis Using dDNP NMR

Kjeldsen, C., J.H. Ardenkjaer-Larsen, and J.O. Duus, Discovery of Intermediates of lacZ beta-Galactosidase Catalyzed Hydrolysis Using dDNP NMR. J. Am. Chem. Soc., 2018. 140(8): p. 3030-3034.


Using dissolution dynamic nuclear polarization, the sensitivity of single scan solution state (13)C NMR can be improved up to 4 orders of magnitude. In this study, the enzyme lacZ beta-galactosidase from Escherichia coli was subjected to hyperpolarized substrate, and previously unknown reaction intermediates were observed, including a 1,1-linked disaccharide. The enzyme is known for making 1,6-transglycosylation, producing products like allolactose, that are also substrates. To analyze the kinetics, a simple kinetic model was developed and used to determine relative transglycosylation and hydrolysis rates of each of the intermediates, and the novel transglycosylation intermediates were determined as better substrates than the 1,6-linked one, explaining their transient nature. These findings suggest that hydrolysis and transglycosylation might be more complex than previously described.