The mature penicillin G acylase fromKluyvera citrophilawas examined by circular dichroism (CD). The far-UV CD spectrum at neutral pH revealed 11 alpha-helix, 44 beta-sheet, 11 beta-turn and 34 random coil. Far-UV and near-UV CD spectra showed that the enzyme presented a high conformational stability under different conditions of pH and salt concentration. The predictive model of Chou and Fasman indicated the presence of several beta-segments that could be arranged in antiparallel beta-sheets, which might explain the structural stability. The near-UV CD spectrum in the presence of penicillin G sulfoxide showed that the binding of this inhibitor to the enzyme resulted in modification of the dichroism of several aromatic residues.
展开▼
