Abstract
Carbon dioxide was found to be required for, and to markedly stimulate, the activity of ACC oxidase enzyme extracted from apple fruit. Without supplemental CO2 enzyme activity was low and variable. The half-maximal concentration CO2 is 0.68% (v/v). Undissociated CO2 rather than CHO−3 serves as the activator of ACC oxidase. CO2 and dithiothreitol act synergistically to activate the enzyme but CO2 activation is independent of dithiothreitol. CO2 increases the Km value for substrates ACC and ascorbic acid several fold while it increases the Vmax about 10-fold. CO2 activation of ACC oxidase resembles that of rubisco, the only other plant enzyme known to be activated by CO2. Whereas CO2 is known to be an inhibitor of ethylene action, it is required to make ACC oxidase catalytically competent to produce ethylene.
Published Version
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