. Biological structure and function; proceedings. Biochemistry; Cytology. RELATIONSHIP BETWEEN REDUCING FACTOR AND REDUCTASE 451 protein used here had been further purified by electrophoresis on paper. With either hydrogen acceptor saturation of the chloroplast system occurred at about the same concentration of added protein and at this saturation level TPN was i • 3 times as effective as metmyoglobin in terms of hydrogen equivalents transferred. This ratio, in different experiments, was found to varv from 1-2 to 1-7 but the variation could not be related to the method used in preparing the le
. Biological structure and function; proceedings. Biochemistry; Cytology. RELATIONSHIP BETWEEN REDUCING FACTOR AND REDUCTASE 451 protein used here had been further purified by electrophoresis on paper. With either hydrogen acceptor saturation of the chloroplast system occurred at about the same concentration of added protein and at this saturation level TPN was i • 3 times as effective as metmyoglobin in terms of hydrogen equivalents transferred. This ratio, in different experiments, was found to varv from 1-2 to 1-7 but the variation could not be related to the method used in preparing the leaf protein. 300 200. 0 1 0 2 mg protein added 03 Fig. 2. Comparison of the activity of pea leaf protein (PPNR further purified by electrophoresis) in catalyzing the reduction of TPN and metmyoglobin. Reaction mixture contained (in 3 ml.) leaf protein as indicated, spinach chloro- plasts (chlorophyll 0-115 irig-), and (in //moles) phosphate buffer pH 77, 90; NaCl, 40; and the following: TPN, 04; ADP, 05; MgCl.,, 15; • metmyo- globin, 0-26. Leaf protein was omitted from the blank cells. Stimulation of TPN reduction by photophosphorylation The reactions shown in Figs i and 2 where TPN was the hydrogen acceptor, were carried out in the presence of adenosine diphosphate (ADP), orthophosphate and magnesium chloride. The presence of this phosphate acceptor system was found to be essential for maximum reduction rates provided that the chloroplasts were at, or near, saturation with respect to added leaf protein. At saturation the additional phosphate-accepting ingredients stimulated the reduction rate 2-5-fold. It was confirmed that inorganic phosphate was incorporated as ATP in the molecular ratio I TPNHo I ATP [7]. This resuh is at variance with the report of Jagen- dorf [8] that no such stimulation of the rate of reduction of TPN during phosphorylation had been detected in three laboratories in the United. Please note that these images are extracted from scanned page images that
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