Conformation of polygalacturonase-II from Aspergillus carbonarius--a spectroscopic study

Solution conformation of polygalacturonase from Aspergillus carbonarius was determined by spectroscopy. UV absorption, second derivative, near-UV CD, fluorescence emission spectra and fluorescence quenching measurements suggest that the tryptophan fluorophores are in a hydrophobic environment. Of the nine tryptophan residues, only one is exposed to the solvent. In the near UV region the enzyme exhibits very weak CD bands, the far UV CD spectrum has a minimum at 218 nm; the enzyme is rich in parallel beta structure. Modification of solvent exposed tryptophan by N-bromosuccinimide resulted in the complete loss of enzyme activity. The enzyme is very sensitive towards urea induced unfolding, with complete loss of activity at 3 M urea concentration.