MULTIPLE FORMS OF PHYTASE IN GERMINATING COTYLEDONS OF CUCURBITA-MAXIMA

Multiple forms of phytase (myoinositol hexaphosphate phosphohydrolase, EC 3.1.3.8) have been isolated in highly purified forms from germinating Cucurbita maxima cotyledons using acetone and ammonium sulphate fractionation, Sephadex gel filtration and ion exchange chromatography on DEAE- and CM-cellulose. Gel filtration produced two peaks of phytase activity; phytase I (high MW) and phytase II (low MW). Phytase I was further resolved into 4 distinct species on CM-cellulose and these were designated phytase IA, IB, IC and ID, according to their elution order. On the other hand, phytase II remained as a single species with a purification of 35-fold. The MWs of each phytase I species were identical (MW 66 500 ± 4000) and they were twice the MW of phytase II (MW 32 400 ± 4000) indicating that I and II may be structurally related. The properties of various molecular forms were compared. The difference in properties between phytase II and phytase I isoenzymes (IA, IB, IC and ID) was more pronounced than that observed among the isoenzymes of phytase I alone. © 1979.