Figure 2.

YhcH encoded by Neu5Ac catabolic operons is an anomerase that facilitates the metabolism of Neu5Ac by Neu5Ac aldolase.A, organization of genomic regions harboring YhcH (green arrow) and NanM (red arrow) in Escherichia coli K12, Haemophilus influenzae KW20, Ruminococcus gnavus ATCC 29149, Vibrio cholerae 01, and Vibrio fischeri ES1. B and C, as shown in Fig. 1, G and H for NanM, YhcH stimulates the utilization of both β- and α-Neu5Ac by NanA. Results shown are means ± SD (n = 3). D–G, ¹H-NMR analysis comparing the anomerase activity of YhcH and NanM. 2,3-EN (1 mM) was incubated at 10 °C in 50 mM deuterated acetate buffer, pH 6, with 20 μM NAD⁺, 1.5 μM YjhC (5), in the absence (in black) or the presence of 0.5 μM NanM (in blue) or 15 μM YhcH (in red). Repetitive NMR spectra were taken at different times following the initiation of the reaction by addition of YjhC. The α (D) and β (E) forms of Neu5Ac were computed from the shift of axial H3 at 1.65 and 1.8 ppm, respectively. The proportion of α-Neu5Ac in the total pool of Neu5Ac was computed from these values (F). The amount of 2,3-EN shown in (G) was calculated from the shift of N5-H in the 8 ppm region. AUC, area under the curve.