A photochemically induced dynamic nuclear polarization study of pancreatic phospholipase A2. NMR assignment of some aromatic residues.

Application of the photochemically induced dynamic nuclear polarization technique to porcine pancreatic phospholipase A2 and its precursor resulted in the observation of nuclear spin polarization for the single tryptophan and 2 tyrosine residues. Using selectively nitrated enzymes, the tyrosine resonances could be assigned to residues 69 and 123. Both tryptophan-3 and tyrosine-69 are of particular interest because they are part of the lipid binding site.