[Extraction and characterization of zeins from kernels of 10 maize cultivars]

The study consisted in the extraction and characterization of zeins of Venezuelan maizes, according to their solubility and molecular properties. The cultivars analyzed were the hybrids Ceniap PB8, Tocoron 127, Arichuna, Obregón, Ceniap 3, Corocito 101 and the varieties Máquina del Ceniap, Venezuela-1 and Venezuela-1 Opaco-2. Zeins were extracted with 70% ethanol and fractionated by two methods: 95% ethanol and column filtration with Sephadex G-200. The molecular weight was determined by electrophoresis in a discontinuous polyacrilamide gel with sodium dodecyl sulfate (PAGE-SDS). The results demonstrated that zeins account for 36.57% of the total protein present in normal corn grain and 9.38% in Opaque-2 corn. Prolamines presented a soluble fraction in 95% ethanol (alpha zeins) which represented 33,12% of zeins and another insoluble (beta zeins) the 66.88%. In column fractionation, three fractions were obtained, two major A and C and another B in minor quantity, which varied in proportion between cultivars. Zeins which were reduced with 2-mercaptoethanol separated into two subunits with molecular weights of 21,300 and 24,300 daltons, whereas unreduced zeins presented large sized aggregates which remained at the origin and large numbers of bands (nine) whose molecular weights oscillated between 24,300 and 87,000 daltons. The electrophoretic patterns of normal maizes were similar, but differ from the pattern of the Opaque-2. In this maize, zeins reduced presented only the band with molecular weight 24,300 daltons and the unreduced zeins showed those with molecular weights of 87,000; 78,500; 48,500 and 24,300 daltons. Reduced alpha and beta are made up of the same basic components of zeins. Likewise unreduced alpha zeins are made up of the same polypeptides as unreduced zeins. The difference between Opaque-2 zeins and normal ones in that they contain more alpha zeins and less polypeptides of high molecular weight.