Characteristics of an<i>Arabidopsis</i>glyoxylate reductase: general biochemical properties and substrate specificity for the recombinant protein, and developmental expression and implications for glyoxylate and succinic semialdehyde metabolism in planta
Bibliographic record
Abstract
Constitutive expression of an Arabidopsis thaliana (L.) Heynh cDNA (GenBank accession No. AY044183 ) in a succinic semialdehyde (SSA) dehydrogenase-deficient yeast ( Saccharomyces cerevisiae Hansen) mutant enables growth on γ-aminobutyrate and significantly enhances the accumulation of γ-hydroxybutyrate. In this report, the cDNA (designated hereinafter as AtGR1) was functionally expressed in Escherichia coli , and the recombinant protein purified to homogeneity. Kinetic analysis of substrate specificity revealed that the enzyme catalyzed the conversion of glyoxylate to glycolate (Km,glyoxylate= 4.5 μmol·L–1) as well as SSA to γ-hydroxybutyrate (Km, SSA= 0.87 mmol·L–1) via an essentially irreversible, NADPH-based mechanism. The enzyme had a 250-fold higher preference for glyoxylate than SSA based on the performance constants (kcat/Km), and with the exception of 4-carboxybenzaldehyde, at least a 100-fold higher preference for SSA than all other substrates tested (formaldehyde, acetaldehyde, butyraldehyde, 2-carboxybenzaldehyde, glyoxal, methylglyoxal, phenylglyoxal, phenylglyoxylate). In vitro assays of SSA reductase activity in cell-free extracts from Arabidopisis revealed its presence throughout the plant, although its specific activity was considerably higher in leaves at all developmental stages and in reproductive parts than in roots. It is proposed that the enzyme functions in redox homeostasis and the detoxification of both glyoxylate and SSA, in planta, resulting in the production of glycolate and γ-hydroxybutyrate, respectively.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".