254 



GERTRUDE E. GLOCK 



CH20P03H2 CH20P03H2 CH20P03H2 CH20P03H2 



Sedoheptulose-7-P Glyceraldehyde-3-P Tetrose-4-P Fructose-6-P 



Fig. 3. Method of formation of fructose-6-phosphate from sedoheptulose-7- 

 phosphate according to Horecker and Smyrniotis.'" 



III. Pentose Phosphate Formation in Photosynthesis 



Calvin and Benson''^ and their co-workers^^ have shown that after very 

 short periods of photosynthesis in C*''02 , phosphoglyceric acid contains 

 most of the radioactivity, this being located almost exclusively in the 

 carboxyl group. Numerous phosphorylated products follow the initial for- 

 mation of phosphoglyceric acid and these have been studied in green algae 

 as well as in preparations from leaves of various higher plants, using C'^ 

 and P^^ as tracers. The identification of small quantities of radioactive 

 compounds has been accomplished by paper chromatography with non- 

 radioactive carriers, coincidence between the radioautograph and the spot 

 produced by the color reaction of a particular carrier being taken as strong 

 evidence for their identity. Sedoheptulose monophosphate, ribose and 

 ribulose monophosphates, and ribulose-1 ,5-diphosphate were among the 

 products detected during the first few seconds of photosynthesis,^^ '^^'^^ 

 most of the pentose phosphate being in the form of ribulose diphosphate. 

 The extreme rapidity with which sedoheptulose phosphate, in particular, 

 is labeled is emphasized by the figures given by Buchanan et al.'^^ After a 

 period of photosynthesis as short as ten seconds by a soybean leaf prepara- 



« M. Calvin and A. A. Benson, Science 1C9, 140 (1949). 



" A. A. Benson, J. A. Bassham, M. Calvin, T. C. Goodale, V. A. Haas, and W. 



Stepka, J. Am. Chem. Soc. 72, 1710 (1950). 

 « A. A. Benson, J. Am. Chem. Soc. 73 2971 (1951). 

 ^^ A. A. Benson, J. A. Bassham, M. Calvin, A. G. Hall, H. E. Hirsch, S. Kawaguchi, 



V. H. Lynch, and N. E. Tolbert, J. Biol. Chem.. 196, 703 (1952). 

 ^8 J. G. Buchanan, J. A. Bassham, A. A. Benson, D. F. Bradley, M. Calvin, L. L. 



Daus, M. Goodman, P. M. Hayes, V. H. Lynch, L. T. Norris, and A. T. Wilson, 



in "Phosphorus Metabolism" (McElroy and Glass, eds.). Vol. 2, p. 440. Johns 



Hopkins Press, Baltimore, 1952. 



