EFFECT OF HYDROGEN PEROXIDE ON THE LIGHTINDUCED CAPACITY OF CARBON DIOXIDE-FIXATION IN GREEN ALGAE

抄録

1. Using intact cells of Chlorella, which had been pretreated with sodium azide (10^-4M to inhibit the activity of catalase, investigations were made-by the “pre-illumination” experiments using C¹⁴O₂ according to Calvin and Benson-on the effect of H₂O₂, upon the photogenic capacity (reduc-ing agent) for CO₂-fixation.
2. It was demonstrated that the level of the C¹⁴O₂-fixing capacity was markedly lowered in the presence of H₂O₂), indicating that the reducing agent was oxidized by H₂O₂. Based on the fact that the same oxidizing effect has been observed with oxygen and quinone, it was inferred that H₂O₂ shares with oxygen and quinone the property of acting as a Hi11 oxidant. The reactivity of these oxidants towards the reducing agent in question was found to be in the order:
quinone<H₂O₂<O₂.
Along the line of reasoning developed in a previous work it was discussed that (i) H₂O₂, is formed in green cells as a result of reaction of O₂, with the reducing agent; that (ii) in normal cells the H₂O₂ thus formed is immediately decomposed by catalase, and that (iii) the inhibitory effect of cyanide upon photosynthesis is due to the inhibition of catalase leading to the accumulation of H₂O₂ which consumes the reducing agent that plays the key role in reducing phosphoglyceric acid to triosephosphate in the mechanism of photosynthesis.
This study was aided by grants from the Nishina Memorial Foundation, the Rockefeller Foundation, and the Ministry of Education. To these bodies we extend our grateful thanks.