2009_Book_FoodChemistry

15.2 Individual Constituents 683
Table 15.14. Classification and properties of gluten proteins
HMW
MMW
HMW Subunits ω-Gliadins LMW
Group x-Type y-Type ω5 ω1,2 α-Gliadins γ-Gliadins LMW
Subunits
Mr × 10 −3 104–124 90–102 66–79 55–65 32 38–42 36–44
(SDS-PAGE) a
Mr × 10 −3 83–88 67–74 44–55 c 34–44 c 28–35 31–35 32–39
(sequence) b
Number of amino 770–827 627–684 n.a. n.a. 262–298 272–308 281–333
acid residues
Content of 4–9% 3–4% 3–6% 4–7% 28–33% 23–31% 19–25%
gluten proteins
Number of 4 7 0 0 6 8 8
cysteine residues
µmolCys/g flour 0.3 0.3 0 0 6.0 6.7 5.0
a Result of electrophoresis.
b Calculated from the amino acid sequence.
c Determined with MALDI-TOF mass spectrometry.
n.a.: not analyzed.
Table 15.15. Amino acid composition a of protein groups of wheat gluten (cultivar Rektor)
HMW
LMW
subunits ω5- ω1,2- subunits α- γ-
of glutenin Gliadins Gliadins of glutenin Gliadins Gliadins
Asx 0.7–0.9 0.3–0.5 0.5–1.3 0.7–1.5 2.7–3.3 1.9–4.0
Thr 3.2–3.8 0.4–0.6 0.8–2.3 1.8–2.9 1.5–2.3 1.6–2.4
Ser 6.4–8.4 2.6–3.3 5.8–6.3 7.7–9.5 5.3–6.6 4.9–6.8
Glx 35.9–37.0 55.4–56.0 42.5–44.9 38.0–41.9 35.8–40.4 34.2–39.1
Pro 11.2–12.8 19.7–19.8 24.8–27.4 14.0–16.2 15.0–16.6 15.8–18.4
Gly 18.2–19.8 0.6–0.8 0.9–2.1 2.3–3.2 1.9–3.2 2.0–3.0
Ala 2.9–3.5 0.2–0.3 0.3–1.3 1.7–2.3 2.6–4.1 2.8–3.5
Cys 0.6–1.3 0.0 0.0 1.9–2.6 1.9–2.2 2.2–2.8
Val 1.6–2.7 0.3 0.6–1.4 3.8–5.3 4.2–4.9 4.4–5.4
Met 0.1–0.3 0.0 0.0–0.3 1.2–1.6 0.4–0.9 1.2–1.6
He 0.7–1.1 4.3–4.7 1.9–3.5 3.6–4.4 3.6–4.6 4.0–4.6
Leu 3.1–4.3 2.7–3.3 3.9–5.3 5.3–7.5 6.5–8.7 6.4–7.3
Tyr 5.1–6.4 0.6–0.7 0.8–1.5 0.9–1.9 2.3–3.2 0.6–1.4
Phe 0.2–0.5 9.0–9.5 7.6–8.1 3.8–5.5 2.9–3.9 4.7–5.6
His 0.8–1.9 1.3–1.4 0.6–1.1 1.3–1.8 1.4–2.8 1.1–1.5
Lys 0.7–1.1 0.4–0.5 0.3–0.6 0.2–0.6 0.2–0.6 0.4–0.9
Arg 1.6–2.1 0.5–0.6 0.5–1.4 1.5–2.1 1.7–2.9 1.2–2.9
a mol % (without Trp).
and 12 in a series of wheat cultivars is shown in
Figs. 15.8 and 15.9. The amino acid sequences
of the subunits 1Dx5 and 1By9 are shown in
Table 15.17.