BIOCHEMICAL AND PHYSIOLOGICAL-STUDIES OF SOYBEAN BETA-AMYLASE

Soybean (Glycine max L. Merr.) seed beta-amylase has been identified a mong the ethanol-soluble proteins, purified and several cDNA clones is olated [Ren et al. (1993) Phytochemistry 33, 535]. Both soybean and ba rley (Hordeum vulgare L.) Beta-amylases were soluble in ethanol soluti ons up to 60%. The solubility of the enzyme decreased with increasing ethanol concentration and dropped sharply between 50 and 60% ethanol. The results showed that beta-amylase is an enzyme which can tolerate e xtensive ethanol treatment at room temperature without losing activity . In soybean seeds, beta-amylase appeared to be located neither in pro tein bodies nor in a membrane fraction. The beta-amylase accumulated i n the developing seed and disappeared from the germinating cotyledons at a rate similar to that of the total seed protein. Soybean beta-amyl ase was resistant to digestion by some proteases, such as trypsin, chy motrypsin and a protease from Staphylococcus aureus V8. Very little of the total amylase activity in soybean leaves and roots was ethanol so luble. In eight other legume seeds tested, amylase activity was very l ow compared to the activity present in soybean seeds.