The degradation of phytin in germinating mung bean seeds has been found to be associated with the increased activity of phytase in the cotyledon. In the differentiated embryo the increase of this activity is very low all throughout the growth periods studied. Phytase appears in the cotyledon during germination. No activity has been detected in the cotyledons of unsoaked seeds. Cycloheximide (10-6 M) inhibits the appearance of phytase by 61% during 24 and 48 hours after the start of germination. This phytase increase is dependent on the synthesis of new RNA in the cotyledon. Synthesisof DNA is not detected inthe cotyledon during germination.Phytase or myoin-ositol hexaphosphate phosphohydrolase (EC 3.1.3.8) which carL hydrolyze myoinositol hexaphosphate to myoinositol and inorganic phosphate has long been known (23). Pears (18) showed that in ungerminated wheat the aleurone portion contained 39%, endosperm 34%, and scutellum 15% of the total phytase activity of the whole seeds. It has also been shown by different groups of workers that phytase activity of different grains increases during germination (1,12,15). Many reports are now available on the characteristics of the enzyme phytase. Nagai and Funahashi (17) reported a phytase, purified 1500-fold from wheat bran, which shows broad substrate specificity at pH 5.0. Gibbins and Norris (6) purified phytase and an acid phosphatase from the cotyledons of germinated Phaseolus vulgaris, the pH optimum of which has been recorded at 5.0. In the present study the activity of phytase in the cotyledons of mung bean seeds (Phaseolus aureus) has been found to be increased after soaking for 24 hr. The pH optimum for this system has been recorded at 7.5 instead of 5.0, the level reported with various preparations from different seeds. Very little phytase activity has been detected in the cotyledons of mung bean seeds after soaking for 6 hr. Regarding the appearance of phytase activity there may be two possibilities: (a) de novo synthesis or (b) activation of enzyme protein already present in the seeds. From the present study it appears that phytase is synthesized de novo in the cotyledon of mung beans after soaking. Research Institute, Pussa, Bihar. "4C-Amino acid mixture, 2-14C-uridine, and 2-'4C-thymidine were obtained from Radiochemical Centre, Amersham, Buckinghamshire, England. Cycloheximide was procured from Nutritional Biochemical Corporation, Cleveland, Ohio. Chromomycin A3 was obtained as a gift from Takeda Chemical Industries, Ltd., Osaka, Japan.
MATERIALS AND METHODSIsolation of Phytate. Phytate was isolated from mung bean by extraction with 1 M HCl04 (4) and separated by gradient elution chromatography on a Dowex 1-Cl column (19).Germination Procedure. The dry seeds of mung beans (Phaseolus aureus) were washed with water for 5 min and then covered with water (3 ml/g of seed) in a large Petri dish with seeds dispersed uniformly over the dish. The Petri dish was then covered, allowing for a little air passage, and kept at 35°in an incubator. After the seeds ...
