In 1957, San Pietro and Lang (1) observed that isolated spinach chloroplasts cause a light-stimulated exchange of the hydrogen of water with the hydrogen at the p position of the nicotinamide ring of oxidized TPN and DPN. Their results showed that there are enzymes in chloroplasts which cause activation of both steric positions of the reduced pyridine nucleotides. Since these early studies, it ...

Spinach grana cause little photoreduction of DPN unless they are supplemented with ferredoxin and TPN reductase. The latter flavoprotein catalyzes a reduction of DPN+ by TPNH, and has been termed a transhydrogenase on the basis of this reaction (2, 3). The results to be presented will show that the flavoprotein transhydrogenase reaction and the Hill reaction both involve hydrogen addition to th...

Hill activity with ferricyanide and nicotinamide adenine dinucleotide phosphate and photoreduction of NADP and methyl red supported by ascorbate and 2,6-dichloroindophenol were studied as a function of the size of chloroplast fragments. Sonic treatment of chloroplasts resulted in a decrease in Hill activity with NADP and ferricyanide. The decrease was accompanied by a change in the dependency o...

The necessity of manganese for the growth of both autotrophic and heterotrophic plants was reported first by Bertrand (5, 6) more than 50 years ago, and the essentiality of manganese for the growth of Chlorella was shown originally by Hopkins (20) of Cornell University in 1930. The relation of manganese to photosynthesis was suspected by McHargue (24) and Bishop (7). However, it was not until 1...

At 5 degree C addition of CO2 or HCO3- to CO (HCO3-)-depleted thylakoids (containing 100 mM formate) initiates, within 10 s, the activation of the Hill reaction in light. In contrast to HCO3- addition, where there is a lag of 6-8 s, the activation by CO2 addition is almost instantaneous. With CO2, prior addition of carbonic anhydrase produces a lag of about 6 s that approaches the lag observed ...

The pesticide PCP was shown to inhibit the Hill reaction in broken chloroplasts (I50 = 15 jam) and to quench chlorophyll fluorescence. Both effects require preillumination. In contrast to the common “phenol-type” inhibitors, neither inhibition of Hill reaction nor chlorophyll fluorescence quench were affected by pretreatment of chloroplast with trypsin instead o f preillumination. An inhibition...

Chloroplasts were treated with 2 m sodium bromide. The resulting particles lost their ATPase activity and chloroplast coupling factor 1 subunits were detected in the supernatant by means of gel electrophoresis and specific antibodies. The chloroplast coupling factor 1 depleted particles show high rates of Hill reaction with pH optimum shifted toward lower pH. The sodium bromide treatment also a...