A mutation doesn't always hurt the enzyme
- The idea
- Predict
- See it
- Why
- Check
The idea
“Any mutation in an enzyme's gene makes the enzyme work worse.”
The mutations in the news cause disease, so mutation sounds like damage. Plenty of others leave the enzyme working fine.
The short version
The mistake: Any mutation in an enzyme's gene makes the enzyme work worse.
What's actually true: It depends on what changed and where. Many mutations do little, some wreck the enzyme, and a few give it a new job.
- The genetic code is redundant, so a silent mutation changes a codon but not its amino acid.
- A missense mutation swaps one amino acid. A look-alike away from the active site usually leaves the fold alone.
- The harmful ones break the fold or the active site, or stop the protein early.
- Most active-site changes hurt. Now and then one fits a new substrate better, which is raw material for evolution.
On the exam: Before calling a mutation damage, ask what it changed and where.