Food Biochemistry and Food Processing

25 Rye Constituents and Their Impact on Rye Processing 575

researchers also purified secalins of low molecular
weight (LMW) (10–16 k) (Charbonnier et al. 1981;
Preston and Woodbury 1975), which is in the same
range as that of wheat low molecular weight gliadin
and barley A hordein.
The S-rich or -secalins are the most abundant
secalins and consist of two major groups of poly-
peptides: 40k -secalins (26% of total secalin frac-
tion) and 75k-secalins (45% of total secalin fraction)
(Gellrich et al. 2003, Shewry et al. 1982). The molecu-
lar weights of 40k- and 75k-secalins are 40 k and
75 k, respectively, as determined by SDS-PAGE
(sodium dodecyl sulfate–polyacrylamide gel elec-
trophoresis), hence their names (Field et al. 1983,
Gellrich et al. 2003, Shewry et al. 1982), and 33 k
and 54 k, respectively, as determined by sedimenta-
tion equilibrium ultracentrifugation (Shewry et al.
1982) or mass spectrometry (Gellrich et al. 2001,
2003). The two groups differ in amino acid compo-
sition, with 75k -secalins having higher contents of
glutamine/glutamate and proline and lower contents

of cysteine than the 40k -secalins (Gellrich et al.

2003, Shewry et al. 1982, Tatham and Shewry

1991).

The -secalins contain two structural domains: an

N-terminal domain rich in glutamine and proline

and consisting of repetitive sequences (Gellrich et

al. 2001, 2004a; Kreis et al. 1985; Shewry et al.

1982), and a C-terminal domain with a nonrepetitive

structure, which has lower glutamine and proline

content and is rich in cysteine (Kreis et al. 1985).

The N-terminal sequences of the 40k - and 75k -

secalins are identical at 16 or 17 of the first 20 posi-

tions (Gellrich et al. 2003, 2004a; Shewry et al.

1982). The N-terminal repetitive domains probably

have a rod-like conformation (Shewry and Tatham

1990), whereas the C-terminal nonrepetitive do-

mains probably have a compact globular conforma-

tion (Shewry and Tatham 1990) rich in 
-helical

structures (Tatham and Shewry 1991). The 75k -

secalins have a lower content of 
-helical structures

than the 40k -secalins (Tatham and Shewry 1991),

Table 25.3.Classification of Rye Proteins

Physiological Classification Osborne Classification Technologically Important Proteins
Nonstorage proteins Albumins Enzymes
Globulins
-amylases
Endoxylanases
Arabinofuranosidases
Xylosidases
Ferulic acid esterases
Proteases
Serine proteases
Metalloproteases
Aspartic proteases
Cysteine proteases
Enzyme inhibitors

-amylase inhibitors
Endoxylanase inhibitors
Protease inhibitors
Storage proteins Secalins -secalins
40k -secalins
75k -secalins
-secalins
HMW secalins

Glutelins -secalins

40k -secalins

75k -secalins

HMW secalins

⎧ ⎪ ⎨ ⎪ ⎩ ⎧ ⎪ ⎨ ⎪ ⎩

⎧

⎨

⎩

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