| Abstrakt: |
Flours of different wheat species (common wheats including winter wheat, spring wheat, and wheat rye hybrid, spelt, durum wheat, emmer, and einkorn) were successively extracted with a salt solution and 60% (v/v) aqueous ethanol. The alcohol extracts (gliadins) were separated by reversed-phase HPLC. Six to nine different ω-gliadins were obtained for each wheat sample and were characterized by their relative amounts, the amino acid compositions, the N-terminal amino acid sequences, and the molecular masses. The wheats investigated showed typical differences in the qualitative and quantitative HPLC patterns. The amino acid compositions of all ω-type gliadins revealed significantly higher proportions of glutamine, proline, and phenylalanine compared with other gluten proteins. These three amino acids accounted for 70 to 86% of the total composition. Typical differences in amino acid compositions, N-terminal sequences, and molecular masses allowed a clear differentiation of the proteins into ω5- and ω1,2-type gliadins; the gliadin fractions of emmer and einkorn contained only the ω5-type, but not the ω1,2-type. ω5-Gliadins were characterized by extremely high proportions of glutamine (52–57 mol %) and relatively high proportions of proline (18–21 mol %) and phenylalanine (9–10 mol %). ω1,2-Gliadins had less glutamine (39–45 mol %) and phenylalanine (6–8 mol %), but much more proline (22–31 mol %). ω5-Gliadins of all wheats except emmer could be assigned to the N-terminal sequence variants SRQLSP or SRLLSP; the typical sequence of emmer ω5-gliadins was SMELQT. The N-terminal sequences of ω1,2-gliadins were characterized by two basic variants beginning with KELQSP or ARQLNP. The wheat rye hybrid had additionally components with the sequence RQLNPS known from ω-secalins of rye. The determination of molecular masses by MALDI-TOF mass spectrometry revealed a range of 44,000–55,000 for the ω5-type and a range of 36,000–44,000 for the ω1,2-type. Thus, the actual masses were by far lower than the values derived from SDS-PAGE mobility. [ABSTRACT FROM AUTHOR] |
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