2009_Book_FoodChemistry

684 15 Cereals and Cereal Products
Fig. 15.6. RP-HPLC of the prolamin fractions of different varieties of cereal (conditions as in Fig. 15.5. Wheat
26–30 min: ω-gliadins, 32–50 min: α-gliadins, 54–71 min: α-gliadins. Rye 21–37 min: γ-secalins, 45–77 min:
γ-secalins. Barley 32–44 min: C-hordeins, 46–66 min: B-hordeins. Oats 49–55 min/62–69 min: avenins; according
to Wieser, Belitz et al., 1989)
15.2.1.3.2 Intermediate Molecular Weight
Group (ω5-Gliadins, ω1,2-Gliadins)
This group of ω-gliadins is characterized by high
values of Glx, Pro, and Phe (Table 15.15). The
proportion of most of the other amino acids is less
than in the other groups and the sulfur-containing
amino acids Cys and Met are either absent or
present only in traces. Total sequences have not
yet been published, but some information is available
on partial sequences. The ω-gliadins can be
divided into two subgroups, the ω5-type and the
ω1,2-type. This nomenclature is based on the
varying mobility on acidic PAGE.
The ω5-gliadins are characterized by an extremely
high content of Glx (ca. 56%) and
a relatively high content of Phe (ca. 9%). Although
the content of Pro (ca. 20%) is lower than
in the ω1,2-type, it is clearly higher than in the
other groups. These three amino acids account
for about 85% of the total protein. ω5-Gliadins
are free of sulfur-containing amino acids and
the content of the remaining amino acids is
comparatively low. It is noticeable that only this
protein type has more Ile (ca. 4.5%) than Leu
(ca. 3%).
The N-terminal sequences consist of the sequence
SRLLSPRGKELHT and are typical of this type