Figure 5

The buffer/pH effects on the pneumococcal sialidase activity. The three sialidases NanA (squares), NanB (circles) and NanC (triangles) showed a variable activity in different buffers (empty markers, citrate/phosphate buffer; plain markers, MES buffer) and at pH values ranging from 4–6.5, with optimum pHs which varied slightly among the three enzymes (NanA 5.5-6.5; NanB 5–5.5; NanC 5–6). These data, measured with either the fluorogenic substrate 4MU-Neu5Ac or the chromogenic substrate p-NP-Neu5Ac, gave comparable results.