... HJ, Tolley SP, Hill CP, Dodson EJ, DodsonG & Moody PCE (1995) Penicillin acylase has a single-amino-acid catalytic centre. Nature 373, 264–268.11 McVey CE, Walsh MA, Dodson GG, Wilson KS ... software pack-age (Accelrys Software Inc., San Diego, CA, USA) (nowDiscovery Studio: http://accelrys.com/products/discovery-studio/). The sulfur in the SO2group was replaced with acarbon ... buffer (pH 7.0). An aliquot of everysample was then used to catalyze the hydrolysis of aconstant amount of the chromogenic substrate 2-nitro-5-phenylacetamidobenzoic acid at 25 °Cin50mm sodiumphosphate...