Amylases from Aleurone Layers and Starchy Endosperm of Barley Seeds

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Abstract
Amylases from incubated aleurone layers or from starchy endosperm of barley seeds (Hordeum vulgare L. cv. Himalaya) were investigated using acrylamide gel electrophoresis and analytical gel filtration with Sephadex G-200. Electrophoresis of amylase from aleurone layers yields seven visually distinct isozymes with an estimated molecular weight of 43,000. Because each isozyme hydrolyzes beta-limit dextrin azure and incorporates calcium-45, they are alpha-amylases. On Sephadex G-200, amylase from the aleurone layers is separated into seven fractions ranging in estimated molecular weights from 45,000 to 3,000. Little or no activity is observed when six fractions are subjected to electrophoresis. Electrophoresis of only the fraction with the estimated molecular weight of 45,000 gave the seven isozymes. The amylases are heat labile and cannot be stabilized by the presence of substrate or by the protease inhibitor, phenylmethylsulfonylfluoride. Electrophoresis of amylase from the starchy endosperm yields nine beta-amylases. Four of these beta-amylases are isozymes with an estimated molecular weight of 43,000. The other five forms of beta-amylase represent molecular aggregates of the four basic beta-amylase monomers. A dimer, a tetramer, and an octamer of beta-amylase can be identified with estimated molecular weights of about 86,000, 180,000 and 400,000, respectively. These estimated molecular weights were confirmed on Sephadex G-200. There are five additional fractions of beta-amylase with estimated molecular weights ranging from 30,000 to 4,000. These fractions are not observed electrophoretically.