A FLUOROMETRIC ASSAY FOR DETERMINING VARIATION OF LYSINE IN WHEAT GLIADIN PROTEINS

An effective method for estimating lysine in wheat gliadin proteins co uld contribute to increasing lysine in wheat. Wheat gliadin proteins w ere separated and collected by reverse phase high performance liquid c hromatography (RP-HPLC). A fluorimetric assay with o-phthalaldehyde (O PA) was used to determine the lysine content of wheat gliadin proteins . The OPA reagent reacts specifically with the amino group of lysine i n protein. Twenty fractions of wheat gliadins were collected and analy zed by the fluorimetric assay. Nine of these fractions were also analy zed for lysine content by an amino acid analyzer. The results obtained from the fluorimetric assay were significantly related to the results obtained from the amino acid analyzer (R = 0.93 for quadratic regress ion of the nine selected gliadin fractions). Lysine content of the whe at gliadins varied from 0.6 to 1.4 percent of the protein. This study determined that the fluorimetric assay could accurately estimate lysin e in wheat gliadin proteins. Identification of high-lysine gliadin sub units could be implemented into a program of breeding for increased ly sine in wheat.