<unk>  catalyzes several different decarboxylation reactions: * L-DOPA to dopamine – a neurotransmitter * L-Phenylalanine to phenethylamine – a trace<unk>  which functions as a neuromodulator * L-Tyrosine to tyramine – a trace<unk>  neuromodulator * L-Histidine to histamine – a neurotransmitter * L-Tryptophan to tryptamine – a trace<unk>  neuromodulator * 5-HTP to serotonin (5-hydroxytryptamine) – a neurotransmitter However, some of these reactions do not seem to bear much or any biological significance. For example, histamine is biosynthesised strictly via the enzyme histidine<unk>  in humans and other organisms. Human serotonin biosynthesis pathway
Aromatic L-amino acid decarboxylase
Phenylalanine hydroxylase
Monoamine oxidase B
Catechol-O-methyltransferase
Tyrosine hydroxylase
Dopamine beta-hydroxylase
Monoamine oxidase A
Monoamine oxidase