Probing the catalytic mechanism of bovine pancreatic deoxyribonuclease I by chemical rescue.

Previous structural and mutational studies of bovine pancreatic deoxyribonuclease I (bpDNase I) have demonstrated that the active site His134 and His252 played critical roles in catalysis. In our present study, mutations of these two His residues to Gln, Ala or Gly reduced the DNase activity by a factor of four to five orders of magnitude. When imidazole or primary amines were added exogenously to the Ala or Gly mutants, the residual DNase activities were substantially increased by 60-120-fold.