title: Inactivation of ribulosebisphosphate carboxylase by modification of arginyl residues with phenylglyoxal.
abstract: Phenylglyoxal rapidly and completely inactivates spinach and Rhodospirillum rubrum ribulosebisphosphate carboxylases. Inactivation exhibits pseudo-first-order kinetics and a reaction order of approximately one for both enzymes, suggesting that modification of a single residue per protomeric unit suffices for inactivation. Loss of enzymic activity is directly proportional to incorporation of [14C]phenylglyoxal until only 30% of the initial activity remains. For both enzymes, extrapolation of incorporation to 100% inactivation yields 4-5 mol of [14C]phenylglyoxal per mol protomer. Amino acid analyses confirm the expected 2:1 stoichiometry between phenylglyoxal incorporation and arginyl modification and suggest that other kinds of amino acid residues are not modified. (Thus, inactivation correlates with modification of 2-3 arginyl residues per protomer). The substrate ribulose bis-phosphate and some competitive inhibitors reduce the rates of inactivation of the carboxylases and prevent modification of about 0.5-1.0 arginyl residue per protomer. Inactivation is therefore a consequence of modification of a small number of residues out of the 35 and 29 total arginyl residues per protomer in spinach and R. rubrum carboxylases, respectively.
mesh_terms: D000447:Aldehydes / Q000031:analogs & derivatives; D001120:Arginine; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors*; D006037:Glyoxal / Q000031:analogs & derivatives; D007700:Kinetics; D010944:Plants / Q000201:enzymology; D012273:Ribulose-Bisphosphate Carboxylase / Q000037:antagonists & inhibitors*
chemical_list: D000447:Aldehydes; D006037:Glyoxal; D001120:Arginine; D002262:Carboxy-Lyases; D012273:Ribulose-Bisphosphate Carboxylase