Properties of adenylate kinase after modification of Arg-97 by phenylglyoxal

Adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3) isolated from porcine skeletal and heart muscle and from rabbit muscle are inactivated when a single arginine residue is modified. In adenylate kinase from pig the modified residue was identified as Arg-97 by peptide-mapping. In native adenylate kinase Arg-97 is located at the bottom of the active site cleft. The protein fluorescence of modified adenylate kinase is reduced. Whereas the addition of AMP, ADP and MgATP quench the fluorescence of native adenylate kinase, the fluorescence of phenylglyoxal-modified adenylate kinase is only affected by ADP and MgATP. This finding is discussed in connection with the structural isomerization observed in native adenylate kinase by X-ray diffraction analysis.