Amino acid compositions of different protein fractions in developing grains of NP 113 barley and its high lysine Notch-2 mutant.

The percent distributions of protein fractions namely albumin + globulin, prolamine and glutelin were studied in developing grains of NP 113 barley and its high lysine mutant Notch-2. During development the percentage of albumin + globulin fraction decreased in NP 113, while those of prolamine and glutelin remained unchanged. The increase in prolamine was substantial from 24 to 31DAA. In Notch-2 the trend followed by albumin + globulin and prolamine was like that in NP 113, while the glutelin fraction showed an increase as compared to 10 DAA. The percent of albumin + globulin was slightly higher in Notch-2 as compared to NP 113. The absolute amount (mg/grain) of all the protein fractions increased during development in both NP 113 and its mutant Notch-2. During the grain development the prolamine content was substantially lower in the mutant than in the parent NP 113. The albumin + globulin content per endosperm was in general also higher in NP 113 than Notch-2. Amino acid analysis of the protein fractions did not reveal significant changes in lysine between NP 113 and Notch-2. Thus, the improvement in lysine in the mutant is primarily due to reduced synthesis of the prolamine fraction and not due to an increase in lysine in the mutant hordein fraction. Part of the improvement in lysine may also be due to increase in the percentage of albumin + globulin fractions which is lysine rich.