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- Title
Kinetic mechanism of a recombinant Arabidopsis glyoxylate reductase: studies of initial velocity, dead-end inhibition and product inhibition.
- Authors
Hoover, Gordon J.; Prentice, Gerald A.; Merrill, A. Rod; Shelp, Barry J.
- Abstract
Kinetic analysis of substrate specificity revealed that a recombinant Arabidopsis protein catalyzes the conversion of glyoxylate to glycolate (Km,glyoxylate = 4.5 μmol·L–1) and succinic semialdehyde (SSA) to γ-hydroxybutyrate (Km, SSA = 0.87 mmol·L–1) via an essentially irreversible, NADPH-based mechanism. In this report, the enzyme was further characterized via initial-velocity, dead-end inhibition and product inhibition studies. The kinetic mechanism was ordered Bi Bi, involving the complexation of NADPH to the enzyme before glyoxylate or SSA, and the release of NADP+ before glycolate or γ-hydroxybutyrate, respectively. It can be concluded that the enzyme functions as a NADPH-dependent glyoxylate reductase (EC 1.1.1.79) or possibly an aldehyde reductase (EC 1.1.1.2), and the kinetic mechanism involved is consistent with that found in members of both the aldo-keto reductase and 3-hydroxyisobutyrate dehydrogenase-related superfamilies of enzymes. Since NADP+ was an effective competitive inhibitor with respect to NADPH (Ki = 1–3 µmol·L–1), it is proposed that the ratio of NADPH/NADP+ regulates enzymatic activity in planta.
- Subjects
ARABIDOPSIS; DYNAMICS; SUCCINATE dehydrogenase; ENZYME kinetics; GAMMA-hydroxybutyrate; ENZYME analysis; ALDEHYDES; PHYSIOLOGICAL control systems; DEVELOPMENTAL biology; ORGANIC compounds
- Publication
Canadian Journal of Botany, 2007, Vol 85, Issue 9, p896
- ISSN
0008-4026
- Publication type
Article
- DOI
10.1139/B07-082