2009_Book_FoodChemistry

686 15 Cereals and Cereal Products
Fig. 15.8. RP-HPLC of the high-molecular (HMW) subunits of the glutelins of different varieties of wheat on
Nucleosil C 8 (60 ◦ C, urea/trifluoroacetic acid/acetonitrile/dithioerythritol; numbering of the peaks: 1–7 (x-type),
8–12 (y-type)); (FAR: Farmer, CWR: Canadian Western Red Spring, APO: Apollo, CHI: Chinese spring; according
to Seilmeier et al., 1991)
A large number of partial and total sequences
are found in the literature. With one exception
(A-gliadin), the total sequences have all been
derived from the corresponding nucleic acids.
Based on present data, the low-molecular gluten
proteins can be assigned to three subgroups
(α-gliadins, γ-gliadins, LMW subunits of
glutenin). As shown in Table 15.18 with three
examples, the total sequences consist of up to
seven differently structured segments: the N- and
C-terminal sequence, segment 1–V. The individual
proteins differ in the N- and C-terminal
sequences, in the recurring sequences (segment
I) and in the Gln-rich sequences (segment IV).
On the other hand, they exhibit long homologous
sequence segments that are low in Pro. These
segments are characterized by the frequent occurrence
of amino acids with charged side chains. In
addition, with a few exceptions, they contain all
the sulfurous amino acids. The M r of this group
of proteins lies in the range of 28,000–39,000
(Table 15.14).
As shown in Table 15.15, the amino acid composition
of the α-gliadins differs on the whole only
slightly from that of the γ-gliadins and LMW subunits
of glutenin. In the case of individual amino
acids, however, significant differences are exhibited.
The content of Tyr (ca. 3%) is considerably