Cereal Chem 51:163 - 172.  |  VIEW ARTICLE
Modified Opaque-2 Corn Endosperms. I. Protein Distribution and Amino Acid Composition.

J. L. Robutti, R. C. Hoseney, and C. W. Deyoe. Copyright 1974 by the American Association of Cereal Chemists, Inc. 

Normal, opaque-2 and modified opaque-2 corn endosperm samples and hand-dissected soft and hard endosperm portions were analyzed for protein content, protein distribution (based on solubility), and amino acid content. In addition, the amino acid content of the extracted protein fractions was determined. Protein distribution was determined by successive extractions with water, ethanol:water (70:30 v./v.), 0.5M sodium chloride, 0.6% 2-mercaptoethanol at pH 10, and 0.5% sodium lauryl sulfate at pH 10. The protein content of opaque-2 endosperms was less than that of their normal counterpart. Protein contents of the modified opaque-2 endosperms were equal to or higher than those of the normal ones. Hard and soft portions of modified endosperms had equal protein contents. The opaque-2 materials had an altered protein distribution; they had higher amounts of water plus salt-soluble protein and lower amounts of alcohol- soluble protein than did normal materials. Modified endosperms had protein distributions that, although closer to opaque than to normal patterns, were significantly different from opaque-2 endosperms. The hard endosperm portion was responsible for that difference. Compared with normal samples, opaque-2 materials had increased levels of lysine, arginine, glycine, and aspartic acid and decreased levels of alanine, leucine, and phenylalanine. The values found for those amino acids in modified endosperms were, in general, intermediate between those values for opaque and normal phenotypes. The amino acid composition of modified soft edosperm was similar to that of opaque phentotypes. The amino acid pattern of modified hard endosperm was not similar to normal or opaque samples but, in general, was intermediate between the two types.