CHLOROPLAST NUCLEOTIDE COENZYMES 

 William L. Ogren and David W. Krogmann 



While the role of pyridine nucleotides and adenosine triphosphate in 

 photosynthesis is accepted without reservation, there is still a deficit of 

 information concerning the distribution of these coenzymes in the plant. 

 Generally, isolated chloroplasts are incapable of energy conserving 

 reactions unless exogenous coenzymes are supplied. This is reasonably 

 explained by assuming the loss of water soluble material from the 

 chloroplast in the isotonic salt or sucrose solutions used for isolation of 

 this subcellular fraction. Chloroplasts prepared in non aqueous solvents 

 present a possibility for the study of water soluble coenzymes which are 

 associated with the photosynthetic apparatus in vivo. Studies of the 

 distribution of the early products of C O fixation indicate that very little 

 water soluble material is lost from the chloroplasts prepared in organic 

 solvents ' . Conversely, studies of enzyme distribution patterns 

 suggest that chloroplasts isolated in non agueous media suffer little 

 contamination with cytoplasmic elements ' . Nevertheless, so new and 

 unconventional a preparation must be viewed with scepticism. A serious 

 objection to chloroplasts prepared in non aqueous media is the virtual 

 absence of Hill reaction or photophosphorylation activities. The hexane- 

 carbon tetrachloride medium used in cell fractionation extracts much 

 lipid from the chloroplasts - almost all the plastoquinone A, a small 

 amount of chlorophyll and nauch else. Recently we have succeeded in 

 partially reactivating the Hill reaction activity to indophenol dye by 

 readdition of the crude lipid obtained from concentrating the isolation 

 mediunn after the chloroplasts have been removed. Representative data are 

 given in Table 1. 



Table I 



Hill Activity of Spinach Chloroplasts 

 Prepared in Non Aqueous Media 



Control 22% 



plus PQA 49% 



plus PQA, plus extracted lipid 67% 



Values are expressed as percentages of 

 the rate of indophenol dye reduction 

 observed with chloroplasts prepared in 

 aqueous 0. 4 M sucrose. 



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