Oxygen-dependent H2O2 production by Rubisco

Oxygen and ribulose-1,5-bisphosphate dependent, H2O2 production was observed with several wild type Rubisco enzymes using a sensitive assay. H2O2 and D-glycero-2,3-pentodiulose-1,5-bisphosphate, a known and potent inhibitor of Rubisco activity, are predicted products arising from elimination of H2O2 from a peroxyketone intermediate, specific to oxygenase activity. Parallel assays using varying CO2 and O-2 concentrations revealed that the partitioning to H2O2 during O-2 consumption by spinach Rubisco was constant at 1/260-1/270. High temperature (38 degreesC), which reduces Rubisco specificity for CO2 versus O-2, increased the rates of H2O2 production and O-2 consumption, resulting in a small increase in partitioning to H2O2 (1/210). Two Rubiscos with lower specificity than spinach exhibited greater partitioning to H2O2 during catalysis: Chlamydomonas reinhardtii (1/200); and Rhodospirillum rubrum (1/150). (C) 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.