Mnemonic to memorise fatty acid synthase complex
The fatty acid synthase (FAS) complex has 7 enzyme activities. A classic mnemonic is:
"Male Kangaroos Don't Actually Earn Their Stripes"
| Letter | Enzyme | Reaction |
|---|---|---|
| M | Malonyl/Acetyl transferase | Loads substrates onto ACP |
| K | Ketoacyl synthase (condensing enzyme) | Condensation (C-C bond formation) |
| D | Dehydratase | Dehydration (removes -OH) |
| A | Acetoacetyl reductase / Ketoreductase | First reduction (β-keto → β-hydroxy) |
| E | Enoyl reductase | Second reduction (enoyl → saturated) |
| T | Thioesterase | Releases final fatty acid (palmitate) |
| S | ACP (Sulfhydryl carrier / acyl carrier protein) | Carries intermediates |
Alternatively, some use the order of reactions per cycle:
"Cats Kindly Drink Real Eggnog Today"
| Step | Enzyme | |
|---|---|---|
| C | Carry substrates | Acyl/Malonyl transferase (loading) |
| K | Knit carbons together | Ketoacyl synthase (condensation) |
| D | Dehydrate | Dehydratase |
| R | Reduce ketone | Ketoreductase (1st reduction) |
| E | Enoyl reduce | Enoyl reductase (2nd reduction) |
| T | Thioesterase releases product | Thioesterase |
Key facts to anchor the mnemonic:
- The complex uses 2 carbons per cycle (from malonyl-CoA)
- 2 NADPH are consumed per cycle (one per reductase step)
- Final product after 7 cycles = palmitate (C16:0)
- The whole complex works as a homodimer in mammals
- ACP (acyl carrier protein) uses a phosphopantetheine arm (same as CoA) to swing intermediates between active sites
A quick memory hook: think of the FAS complex as a "4-step cycle after loading" - Load → Condense → Ketoreduction → Dehydration → Enoyl reduction → repeat, then release with thioesterase.
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