Cereal Chem 53:805 - 819. | VIEW
Albumin Alpha-Amylase Inhibitor Families from Wheat Flour.
R. DePonte, R. Parlamenti, T. Petrucci, V. Silano, and M. Tomasi. Copyright 1976 by the American Association of Cereal Chemists, Inc.
When submitted to gel filtration on a Sephadex G-100 column, albumins from 70% extraction wheat flour gave three peaks whose molecular weights were 60,000, 24,000, and 12,000. These three peaks were coded as Peaks II, III, and IV, respectively, to stress the absence in this albumin fraction of Peak I (excluded in the column void volume) which was the main peak observed when albumins from whole wheat flour were analyzed under identical experimental conditions. Peaks II and III were active in inhibiting human saliva and Tenebrio molitor L. alpha-amylases, whereas Peak IV only inhibited the insect amylase. After treatment with sodium dodecyl sulfate in the presence or absence of beta-mercaptoethanol, the molecular weight of Peak IV was unaffected, whereas about 80% of Peak II and 95% of Peak III dissociated into subunits with a molecular weight identical to that of Peak IV. The extensive dissociation of Peaks I and II was reversed upon removal of the detergent by ion-exchange chromatography, but the inhibitory activity toward alpha- amylase was restored only when treatment with the detergent had been carried out in the absence of beta- metcaptoethanol. When submitted to polyacrylamide gel electrophoresis, Peaks II and III were found to be heterogeneous. Ten anodic components at pH 8.5 and seven cathodic components at pH 4.3 were observed in Peak III; Peak II showed 5 components at both acidic and alkaline pH values. Peak III was fractionated into four peaks by means of preparative gel electrophoresis at pH 8.5. Although no isolation of individual components could be achieved, it was possible to show that all the components of Peak III which moved toward theanode at alkaline pH (about 95% of the total) were active in inhibiting human saliva and T. molitor L. alpha-amylases. moreover, they showed very similar amino acid compositions and circular dichroism spectra in the far and near ultraviolet. These results indicate that the components of Peak III constitute a family of closely related albumins (coded as 0.19 family from the electrophoretic mobility of the main component).