Psilocybin is made naturally inside certain mushroom species—especially those in the Psilocybe genus—through a series of enzyme-driven biochemical reactions.

Here’s how the process works in simple terms:

1. Starting material: Tryptophan
   The process begins with tryptophan, an amino acid that mushrooms obtain from their normal metabolism.

2. Conversion to tryptamine
   An enzyme called tryptophan decarboxylase removes a carboxyl group from tryptophan, converting it into tryptamine.

3. Formation of psilocin
   Tryptamine is then modified by another enzyme, tryptamine 4-hydroxylase, which adds a hydroxyl (–OH) group. This produces psilocin, the compound responsible for psychedelic effects.

4. Final step: Phosphorylation
   Finally, the enzyme psilocybin synthase adds a phosphate group to psilocin. This chemical change converts psilocin into psilocybin.

In short, psilocybin is produced when mushrooms enzymatically transform the amino acid tryptophan into tryptamine, then into psilocin, and finally into psilocybin by adding a phosphate group.