Biocarbonate Effect on the Photophosphorylation Catalyzed by Chromatophores Isolated from Chromatium Strain D: XII. Structure and Function of Chloroplast Proteins.

Photophosphorylation catalyzed by chromatophores prepared from Chromatium strain D was stimulated by bicarbonate. The stimulative effect was pH dependent and the lower the pH the more marked the activation. At pH 8.0, bicarbonate (8 mm) exhibited a negligible effect, whereas at pH 7.0 approximately a 5-fold activation was observed. The apparent activation constant of bicarbonate was determined to be approximately 10.2 mm, at which concentration approximately a 7-fold activation of photophosphorylation was observed.