Characteristics of Thiol:Protein Disulfide Oxidoreductase from Wheat (Triticum aestivum L.) Grain

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S. V. Osipova^*, A. V. Permyakov, T. N. Mitrofanova, L. V. Dudareva, and V. A. Trufanov

Siberian Institute of Plant Physiology and Biochemistry, Siberian Division of the Russian Academy of Sciences, P.O. Box 1243, ul. Lermontova 132, 664033 Irkutsk, Russia; fax: (3952) 510-754; E-mail: gluten@sifibr.irk.ru

^* To whom correspondence should be addressed.

Received June 30, 2004; Revision received November 18, 2004

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Biochemical properties of a homogenous preparation of thiol:protein disulfide oxidoreductase (TPDO, EC 1.8.4.2) isolated for the first time from mature wheat (Triticum aestivum L.) grain were studied. According to polyacrylamide gel electrophoresis data, the molecular weight of TPDO is around 167 kD, the enzyme consisting of two subunits of 77 and 73 kD, which differentiates TPDO from known enzymes of SH/SS-metabolism of wheat caryopses. In substrate specificity and enzymatic characteristics (pH and temperature optima) TPDO is similar to analogous enzymes of animal tissues. Inhibition of disulfide reductase activity by alkylating agents and heavy metal ions suggests the participation of active center SH-groups in the catalytic act and classes the enzyme as a member of the thioredoxin superfamily. The SS-reductase reduces aggregating capacity of acetic acid-soluble fraction of wheat storage proteins. The proposed physiological role of TPDO is participation in creation and regulation of SH/SS-status of wheat endosperm proteins and formation of the rheological properties of gluten.

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KEY WORDS: thiol:protein disulfide oxidoreductase, molecular mass, substrate specificity, inhibition, enzymatic properties, wheat storage proteins, aggregation

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