Fig. 3.

Reaction kinetics of 3- or 6-sialyllactose and SiaPG under different conditions. Variable concentrations of sialyllactose were exposed to SiaPG, under conditions mimicking physiological (pH 7.4 200 mM NaCl). Reactions were quenched by commencing the thiobarbituric acid assay at 1, 2 and 3 min, and the rate of Neu5Ac release determined by application of a Neu5Ac standard curve. (a) Michaelis–Menten plot, rate of 4-MU release (V0, µmol MU released min⁻¹ mg⁻¹ SiaPG), plotted against [3- or 6-sialyllactose] (µM) using Prism 7 (GraphPad). Error bars, sem. (b) Table summarizing Michaelis–Menten reaction kinetics and catalytic efficiency of SiaPG and MU-NANA, the table includes the k _cat (4-MU release min⁻¹), and k _cat/K_M (µM min⁻¹). Data shown represent the mean (±sd) of one experiment, where each condition was repeated three times per experiment.