Succinic semialdehyde dehydrogenase of wheat grain |
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Authors: | L. Galleschi M. G. Tozzi I. Cozzani C. Floris |
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Affiliation: | (1) Institute of Botany, University of Pisa, Via Luca Ghini, 5, I-56100 Pisa, Italy;(2) Laboratory of Biochemistry, Faculty of Science, University of Pisa, Via Luca Ghini, 5, I-56100 Pisa, Italy |
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Abstract: | Succinic semialdehyde dehydrogenase (EC 1.2.1.16) was purified 74-fold from wheat grain (Triticum durum Desf.). The enzyme appears quite specific for succinic semialdehyde (SSA). Both NAD and NADP support the oxidation of the substrate, but the former is 7-fold more active than the latter. The optimum pH for activity is around 9; the enzyme is stable in the pH range 6–9 and retains its whole activity up to 40°C. The enzyme activity is strongly dependent on the presence of mercaptoethanol, other thiol compounds being much less effective. Kinetic data support the formation of a ternary complex between enzyme, substrate and coenzyme. The Km for SSA and for NAD are 7.4x10-6 M and 2x10-4 M, respectively. The molecular weight of the enzyme protein was estimated by gel-filtration to be about 130,000.Abbreviations GABA -aminobutyric acid - GABA-T -aminobutyric acid transaminase - ME mercaptoethanol - SSA succinic semialdehyde - SSA-DH succinic semialdehyde dehydrogenase |
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Keywords: | Aldehyde oxidation Succinic semialdehyde dehydrogenase Thiol compounds Triticum |
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