Catalyzes the decarboxylation of tryptophan to tryptamine. Tryptamine is a neurotransmitter that induces the release of serotonin, which is suggested to modulate gastrointestinal motility. Therefore, the tryptophan decarboxylase from the gut bacteria Clostridium sporogenes (strain ATCC 15579) may influence host brain and behavior. Has weak activity with tyrosine. Activity against phenylalanine is undetectable. H(+) + L-tryptophan = CO2 + tryptamine Inhibited by (S)-alpha-fluoromethyltryptophan. kcat is 1200 min(-1) with tryptophan as substrate. In vitro, tryptamine is excreted into the extracellular fluid, suggesting that the bacterium has the potential to excrete tryptamine in the host gut lumen. Belongs to the group II decarboxylase family.