Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/1998
Publication Date: N/A
Interpretive Summary: Minerals bound to phytic acid as well as the phosphorus of phytic acid are of generally low bioavailability unless the phytate is hydrolyzed by the enzyme phytase. Phytase was quantified in selected fresh vegetables and purified from green onions. The substantial amounts of phytase discovered in fresh green leafy vegetables may have a significant role in digesting dietary phytic acid. Vegetable phytases may be an alternative to the seed and fungal phytases that are currently used by industry to break down phytic acid in foods and feeds.
Technical Abstract: Levels of phytase comparable to those in wheat germ were detected in a variety of fresh green vegetables. The highest activity was found in scallion leaves and purified 360-fold to an activity of 27 micromol per min per mg at 37 degrees C. Scallion phytase had a Km of 200 micromolar for inositol hexakisphosphate and maximum activity at pH 5.0. The enzyme had a temperature optimum at 42 degrees C and was inactivated by preincubation for 10 min at 58 degrees C. The initial product formed from phytic acid eluted from an ion chromatography column at the retention time of inositol 1,2,3,5,6-pentakisphosphate, and the specificity was not altered by the presence of a ten-fold excess of iron or magnesium. Vegetable phytases may be an alternative to seed and fungal phytases used in the processing of food and feed products.