FIG 1.

Incubations of 100-μl samples, containing 1 mM 4MU-Neu5Ac, 1 mM lactose, and 100 ng TcTS. The buffers used were Na-citrate (pH 4.5 to 5.5), HEPES (pH 6.0 to 7.0), and Tris-HCl (pH 7.5 to 9.0). Conversion analyses were carried out by HPAEC-PAD. All data represent averages from duplicate experiments, and the 100% value represents 1.0 μmol · min⁻¹ · mg⁻¹ (A) and 4.0 μmol · min⁻¹ · mg⁻¹ (B and C). (A) Temperature-dependent activity of TcTS was determined over the range of 15 to 50°C at pH 7.5. (B) Optimal pH for trans-sialidase activity of TcTS in the pH range 4.5 to 9.0 at 25°C. (C) Heat stability/residual activity of TcTS, determined by preincubating the enzyme at a range of 15 to 50°C for 30 min in the presence (open circles) or absence (closed circles) of 1 mg/ml bovine serum albumin (BSA); analysis was done at pH 5.0 and 25°C.