Rose Bengal as a specific photosensitizer for a histidine residue at the triphosphopyridine nucleotide binding site of 6-phosphogluconate dehydrogenase.

Rose Bengal is a potent inhibitor of 6-phosphogluconate dehydrogenase from Candida utilis and mediates the photoinactivation of the enzyme. The experiments reported in this paper indicate that photoinactivation occurs only when the dye is bound to the TPN binding site of the enzyme. Since the photoinactivation is correlated to the specific oxidation of only 2 residues of histidine, it can be assumed that this amino acid is located at the TPN binding site of 6-phosphogluconate dehydrogenase. These results are a new application of the technique of active site-specific photooxidation.