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Purification and Characterization of a New Class of Insect α‐Amylase Inhibitors from Barley
Author(s) -
Zhang Ningyan,
Jones Berne L.,
Tao H. Peggy
Publication year - 1997
Publication title -
cereal chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.558
H-Index - 100
eISSN - 1943-3638
pISSN - 0009-0352
DOI - 10.1094/cchem.1997.74.2.119
Subject(s) - chemistry , amylase , amino acid , biochemistry , storage protein , hordeum vulgare , trypsin , gel permeation chromatography , molecular mass , high performance liquid chromatography , enzyme , chromatography , poaceae , botany , biology , gene , organic chemistry , polymer
Barley seeds contain proteins that apparently protect them against attack by microorganisms and insects. Studies of these barley defensive proteins may lead to the development of barleys with improved natural resistance to pests. We have purified two low molecular weight proteins, designated BIα1 and BIα2, from barley grain, using ion‐exchange chromatography and reversed‐phase and gel‐permeation high‐performance liquid chromatography (HPLC). Both BIα1 and BIα2 inhibited insect (yellow meal worm, Tenebrio molitor ) α‐amylase activities. For the T. molitor α‐amylase, the IC50 values of BIα1 and BIα2 were 80 μg/mL (12.5 μ M ) and 34 μg/mL (6.8 μ M ), respectively. Neither protein inhibited either human salivary α‐amylase, barley α‐amylase, or trypsin activities. N‐terminal amino acid sequences of the inhibitors were highly homologous with those of the plant proteins called defensins . The first 20 N‐terminal amino acids of BIα2 were identical to those of γ‐hordothionin, but neither BIα1 nor BIα2 protein showed any homology with the chloroform‐methanol (CM) soluble protein amino acid consensus sequence. The two inhibitors therefore apparently comprise another group of low molecular weight barley proteins that inhibit the α‐amylase activities of some insects that attack cereal grains.