Catalase-peroxidase (KatG) Structure and Function
Bibliographic record
Abstract
Catalase-peroxidases, or KatGs, are fascinating multifunctional enzymes the first of which, from Escherichia coli, was characterized in 1979. The first crystal structure of a KatG from Haloarcula morismortui was reported in 2002 as a homodimer in which the N- and C-terminal domains of each subunit are structurally very similar. The core structure and heme cavity of the N-terminal domain bear a strong resemblance to plant peroxidases, and the catalytic ability is provided by a crosslinked structure involving the side chains of a methionine, a tyrosine and a tryptophan in a reversible association with a mobile arginine. The indole N–H of the tryptophan of the Met-Tyr-Trp adduct is reversibly modified with a perhydroxy modification (Trp–OOH) formed in a rapid reaction with molecular oxygen or as an intermediate in the catalytic reaction cycle. KatGs also activate the anti-tubercular pro-drug isoniazid or isonicotinic acid hydrazide by converting it to isonicotinyl-NAD. Several isoniazid binding sites have been identified in different KatGs, all in locations where electron transfer can feed electrons to the heme for superoxide synthesis, required in the activation process, and the peroxidatic reaction.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 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) | 0.003 | 0.000 |
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 teacher head, 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".