Xcvii. Hexosephosphates Produced by Higher Plants.'

THE fact that phosphates stimulate the respiratory sugar metabolism in higher plants suggests that the formation of phosphoric esters may occur as part of this process. Stoklasa et al. [1904-1913] obtained cell-free zymase-like preparations from peas, beet-roots, potatoes etc., which actively fermented sugars. Bodnar [1916] confirmed these results under strictly aseptic conditions, since some investigators had attributed Stoklasa's findings to bacterial contamination. Evidence of phosphorylation was first given by Bodnar [1925] who demonstrated that inorganic phosphate disappeared when added to ground peas in presence of toluene. His results were confirmed by Zalesky and Pissarjewski [1927] who did not however regard this process as a necessary step in the respiration and attributed the stimulation to alkalinity of the phosphate rather than to the formation of phosphoric esters. More recently, Rao [1935] has prepared active cell-free aqueous extracts by plasmolysing fermenting peas with light petroleum and states that in such extracts the decomposition of sugar and the phosphorylation are concomitant processes. While Bodnair's findings indicated the possible parallelism between carbohydrate metabolism in the higher plants and in yeast or muscle [Harden, 1932; Bodnair and Tank6, 1929], little evidence was available regarding the nature of the compounds formed during the phosphorylation. It is known that when preparations of germinating peas, beans, barley etc. are allowed to act upon the hexosediphosphoric acid of Harden and Young products are formed which are characteristic of sugar breakdown in yeast or muscle [Neuberg and Gottschalk, 1924; 1925; Neuberg and Kobel, 1929; 1930; 1934, 1; Baba, 1935]. Moreover, with phosphoglyceric acid as a substrate, pyruvic acid is formed [Neuberg and Kobel, 1934, 2]. Barrenscheen and Albers [1928] found that the acid-soluble phosphorus increased during assimilation in irradiated Elodea canadensis and during germination of rye. A phosphoric ester was isolated by Barrenscheen and Pany [1930] from the phosphorylated products formed when Elodea was kept in a dilute solution of sugar and inorganic phosphate for an irradiation period of 4 hours. In its composition (Ba, P) the ester resembled a hexosemonophosphate, but it differed from the Robison ester [Robison, 1922] in possessing a much lower reducing power (iodimetric, 3-2 %; H.J. 3.5 %). These investigators also isolated the barium salt of a phosphorylated octaamylose from the germ plants of wheat. This substance gave a high dextrorotation, [oc] D°+ 44.90, and after hydrolysis by takadiastase of its magnesium salt, yielded a hexosemonophosphoric ester having H.J. 22-6 % and [cx] °-4 3°. On hydrolysis by bone phosphatase the monophosphate yielded fructose, which was identified by means of its methylphenylosazone. The authors also found that the synthetic phosphorylated