The protein disulfide isomerase (PDI) enzyme is involved in the formation of disulfide bonds. Here we attempted to purify PDI from wheat grain (Triticumaestivum cv. Haruyutaka). As a result of DEAE-Sepharose Fast Flow and affinity chromatography purification, 30.74units of PDI activity／100g of wheat grain were observed in the adsorbed fraction from the affinity chromatography column. The molecular weight of this fraction was63kDa as determined by SDS-PAGE analysis. N-terminal amino acid sequencing of this63－kDa protein showed that the sequences of wPDI and this63－kDa protein shared79%identity. On the basis of this result, we assumed that the63－kDa protein that we purified from wheat (Haruyutaka) grain is the same as wPDI, which we used for genetic information, and that our expression of this protein was successful.
