TABLE 2

Rate constants of SULT1A1 wild-type and monomeric mutant using PAP and pNPS as substrates

The reaction mixture in final volume of 1 ml consisted of 100 mM bis-tris propane at pH 7.0, 50 μM β-naphthol, and 1 mM pNPS plus PAP (5–1000 nM) or 2 μM PAP plus pNPS (0.05–20 mM), respectively. Enzyme (40 nM dimer and 80 nM monomer, respectively) was added to start the reaction. The reaction was carried out for 2 min in a cuvette with path length of 1 cm at 25°C in a Hitachi UV/Vis-3300 spectrophotometer for detection of an absorption change at 400 nm.