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Plant Physiology 66:308-312 (1980)
© 1980 American Society of Plant Biologists

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Articles

Isolation and Characterization of Thiamin Pyrophosphotransferase from Glycine max Seedlings 1

William T. Molin2 and Roger C. Fites3

Department of Botany, North Carolina State University, Raleigh, North Carolina 27650

Thiamin:ATP pyrophosphotransferase (EC2.7.6.2) activity from soybean (Merr.) seedlings grown for 48 hours was determined by measuring the rate of [2-14C]thiamin incorporation into thiamin pyrophosphate. With partially purified (11-fold) enzyme, optimal activity occurred between pH 7.1 and 7.3, depending on the buffer system that was used. Assays were routinely conducted at a final pH of 8.1 in order to minimize interference from competing reactions. Enzyme activity required the presence of a divalent cation, and a number of nucleoside triphosphates proved to be active as pyrophosphate donors. Apparent Km values of 18.3 millimolar and 4.64 micromolar were obtained for Mg·ATP and thiamin, respectively. Among the compounds tested, pyrithiamin and thiamin pyrophosphate were most effective in inhibiting thiamin pyrophosphotransferase activity. Based on Sephadex G-100 gel filtration, soybean thiamin pyrophosphotransferase has a molecular weight of 49,000.

2 Present address: Department of Biochemistry and Nutrition, Virginia Polytechnic Institute and State University, Blacksburg, Va. 24061.

3 To whom reprints requests should be addressed.

1 This work was supported in part by the North Carolina Soybean Producers Association and is Paper No. 6094 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, N. C.






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Copyright © 1980 by the American Society of Plant Biologists