Phytase in Lower Fungi
نویسنده
چکیده
The occurrence of an enzyme which catalyzes the cleavage of phytin into inosite and phosphoric acid was first noted in rice bran by Suzuki, Yoshimura and Takaishi.1 These investigators found that when rice bran was suspended in water and left for several days at room temperature the greater part of the organic phosphorus went into solution, and at the same time phosphoric acid was formed at the expense of the organic phosphorus compound. The same change was also observed in the organic phosphorus compound present in the oil cake of Bras&a napm. The increase in inorganic phosphorus was in both cases so striking as to suggest the possibility that an enzyme might be responsible for the reaction. This was proved beyond all question by extracting some fat-free rice bran with water, removing the phosphates by means of barium chloride, precipitating the enzyme with alcohol, and testing its activity in vitro upon a phytin solution. Both phosphoric acid and inosite were identified in this case as cleavage products of the phytin. It is probable that where phytin occurs in plants it is usually accompanied by the enzyme phytase which under proper conditions effects the decomposition of this phosphatide. In fact, the enzyme seems to be more widely distributed in nature than phytin itself. McCollum and Hart2 tested various animal tissues for phytase, and found that liver and blood contained this enzyme, although extracts of kidney and muscle did not. Despite the fact that inosite is a well known constituent of animal tissues, phytin has not yet been isolated from them.
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