Cereal Chem. 70:667- 671   |  VIEW ARTICLE

Differences in Kafirin Composition During Endosperm Development and Germination in Sorghum Cultivars of Varying Hardness.

H. Mazhar and A. Chandrashekar. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

The content and composition of kafirins in hard- and soft-endosperm sorghum cultivars were studied during endosperm development and germination. Enzyme-linked immunosorbent assay, sodium dodecyl sulfate- polyacrylamide gel electrophoresis, nonequilibrium pH gradient electrophoresis, and nitrogen analysis were used in the study. Kafirins extracted with 60% (v/v) t-butanol (Kafirin 1) increased slightly during endosperm development in both the cultivars. The predominant Kafirin 1 protein was alpha-kafirin. Kafirins extracted with 60% (v/v) t-butanol plus 5% (v/v) 2-mercaptoethanol (Karifin 2) increased more in both cultivars.The hard-endosperm kernels deposited the alpha- and gamma-kafirins up to 14 days after anthesis (DAA). In the soft-endosperm kernels, these kafirins were deposited after 21 DAA. The beta-kafirin was synthesized maximally after 21 DAA in both cultivars. An increased level of beta-kafirin was noted in the hard-endosperm kernels at all stages of development. The beta- and gamma-kafirins became progressively cross-linked as endosperm development proceeded. Hard-endosperm kernels had more cross-linking than did soft-endosperm kernels. Qualitative differences within the individual kafirins during endosperm development were revealed by nonequilibrium pH gradient electrophoresis. A basic beta-kafirin isoform was faintly stained in extracts of soft-endosperm kernels. During germination the beta- and gamma-kafirins were extensively degraded in both cultivars. More kafirin degradation occurred in the soft-endosperm kernels than in the hard-endosperm kernels. Nonequilibrium pH gradient electrophoresis indicated a differential breakdown of the individual kafirins during germination. Differences in the rate, type, and content of kafirin deposition affected protein degradation during germination.