INFLUENCE OF CO2 ON ACC OXIDASE ACTIVITY FROM ROOTS OF SUNFLOWER (HELIANTHUS-ANNUUS) SEEDLINGS

The activity of the ethylene forming enzyme ACC oxidase was assayed in vitro under aerobic conditions with and without high levels of exogenous CO2, varying the parameters of ascorbate, pH, temperature, ACC and O2. It was found that CO2 had no effect on the temperature optimum of the enzyme. High CO2 increased the optimal ascorbate level, and radically increased the V(max) of the enzyme. Five per cent CO2 doubled the K(m) for ACC and decreased the K(m) for O2 Slightly. The pH optimum of the enzyme was shifted lower with high CO2. The possibility that CO2 may have an influence on ethylene biosynthesis by tissues in vivo is discussed.