Why acetaldehyde kills the DERA aldolase
Crotonaldehyde, the acetaldehyde aldol product, covalently bridges catalytic K167 to nearby C47; a C47M mutant survives 300 mM acetaldehyde.
Source
Mechanism-based inhibition of an aldolase at high concentrations of its natural substrate acetaldehyde: structural insights and protective strategies
Study at a glance
- Design
- Animal / in-vitro — Crystallography, 13C NMR, and a C47M mutant of E. coli DERA in concentrated acetaldehyde
- N
- Enzyme kinetics and structures rather than a biological sample N
- Population
- E. coli deoxyribose-phosphate aldolase and orthologues
- Outcome
- Crotonaldehyde covalently inactivates DERA via K167–C47; C47M retains activity in 300 mM acetaldehyde
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Inspect source passages
Why acetaldehyde kills the DERA aldolase
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
C47M loses no activity after 16 h in 300 mM acetaldehyde.
In contrast, the C47M mutant did not lose any activity even after 16 h in the presence of 300 mM acetaldehyde.
The variant retains 60 ± 5% of wild-type activity; Tm is 65.1 °C versus 66.6 °C for wild type.
Biochemical characterization of the new variant showed that it retains 60 ± 5% of the wildtype activity towards its natural substrate, and the melting temperature of 65.1 °C suggest a similar thermostability as found for wildtype DERA (66.6 °C).
What they did
Authors combined crystallography, 13C NMR, and a C47M mutation to learn how E. coli DERA dies in concentrated acetaldehyde and how to protect it for synthesis.
What they found
After 200–300 mM acetaldehyde the enzyme is irreversibly inactivated. Crotonaldehyde forms a Schiff base at K167 and a covalent link to C47. Crotonaldehyde inhibits more than 100-fold more potently than acetaldehyde (1 mM, <1 h). C47 is conserved in 91% of orthologues. C47M keeps 60 ± 5% activity and loses none after 16 h in 300 mM acetaldehyde.
The limits
What it doesn't show
The work does not deliver a process-scale biocatalytic plant or map every aldehyde side product; only one protective mutation is fully characterized.
Key terms
- DERA
- 2-Deoxy-D-ribose-5-phosphate aldolase, an acetaldehyde-dependent C–C enzyme.
- Crotonaldehyde
- α,β-unsaturated aldehyde from dehydrating the acetaldehyde aldol dimer.
- Mechanism-based inhibition
- A substrate-derived product that covalently inactivates the enzyme.
- C47M
- Mutation that removes the nucleophilic cysteine and confers acetaldehyde resistance.
- Schiff base at K167
- Imine between the catalytic lysine and the donor aldehyde.
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The mechanism-based inhibitor is:
Common questions
What is the true inhibitor?
Crotonaldehyde, not acetaldehyde itself.
Which residues are covalently linked?
Catalytic K167 and nearby C47.
Does C47M still work?
Yes—about 60% wild-type activity and no loss after 16 h in 300 mM acetaldehyde.
How common is C47?
Present in 91% of aligned orthologues.
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