• Journal of Plant Biology
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• v.39 no.1
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• pp.41-48
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• 1996

Two forms of homo serine dehydrogenase have been isolated from 8-day-old cotyledons of Canavalin lineata by a heat denaturation, ammonium sulfate fractionation, DEAE-8ephacel ion exchange and Sephacryl 8-300 gel filtration chromatographies, and Pro cion red dye, Cibacron blue dye and Resource Q column chromatographies. The molecular weights of T -form (threonine-sensitive) and K-form(threonine- insensitive) were estimated to 230 kD and 135 kD, respectively. In the presence of 10 mM threonine, the activity of T-form was inhibited with almost 70%, but that of K-form was not at all. The Km values tor homo serine of T- and Kform were 1.6 mM and 0.3 mM, respectively. The Km values for NAD of T- and K-form were 2.34 mM and 0.03 mM, respectively. And Km values for NADP of two isozymes were the same as 0.01 mM. The activities of T- and K-form were markedly stimulated up to 4.9and 2.8-fold, respectively, by 400 mM KCI. The partial purified(gel filtration) enzymes(Tform and K-form) can be reversibly converted.verted.