On phytic acid, its importance in metabolism and its enzymic cleavage in bread supplemented with calcium.

Phytic acid, a hexaphosphoric ester of inositol, is found in all plant seeds examined, in grains as well as in oilseeds, and undoubtedly represents a store of phosphoric acid that is hydrolyzed in sprouting. For this reason green plants never contain considerable amounts of phytic acid. The cleavage in the seed is evidently caused by a specific enzyme called phytase, but other phosphatases from plant tissue are able to split the substance to some degree. In most cases no phytase activity is found in resting seeds. The enzyme seems to be formed during sprouting of the seeds. Wheat and rye, and to a certain extent barley and buckwheat, are, however, exceptions from this rule. If the whole flour of these grains is suspended in a buffer solution at pH 5 and left at a temperature of 400 for 2 hr. all the phytic acid in wheat and rye, and a considerable part of the acid in barley and buckwheat, is split into inositol and free phosphoric acid. In flours of any other seeds examined no cleavage of phytic acid takes place under these conditions. Experiments with pure phytase preparations have proved the conditions mentioned to be optimal, and confirm the conclusion that these grains do not contain phytase. Table 1 shows the results of investigations by Pedersen (1940) in M0llgaard's laboratory. Total P was in the experiments of Pedersen and in other experiments referred to in this paper determined by destruction of the substance with concentrated sulphuric' and nitric acids and precipitation as ammonium phosphomolybdate; this was heated at 5500 to form phosphomolybdic acid (Hansen & Grasholm, 1935). The phytic P was determined by extraction with 0-5N-HCI and precipitation as iron phytate; this was decomposed with NaOH, and the P in the dissolved sodium phytate was determined according to the method for total P (Pedersen, 1940). Ca was determined by destruction with concentrated sulphuric acid, dissolution of the ash in diluted hydrochloric acid and precipitation as oxalate, which was titrated with permanganate (Hansen & Graesholm, 1935). Wheat Wheat bran