L Tryptophan is an important precusor substance of auxin biosynthesis in plant. It has the similar structure of IAA. It widely exists in higher plant. There are two ways to synthetic auxin. The first is tryptophan oxidizes and deaminize and form indole acetone,then decarboxylation and form IAAId; Under the corresponding enzymes IAAId oxsidizes indoleacetic acid. The second way is decarboxylation and form to tryptamine then tryptamine oxsidize deamination finally forms tryptophan.

1. L Tryptophan is an important nutrient.
2. L Tryptophan takes part in the renewal of animal blood plasma protein in the body
3. L Tryptophan helps nicotinic acid and the synthesis of hemoglobin. It can significantly increase antibody in pregnant animals baby.
4. L Tryptophan can promote lactation of cows and sows.
5. L Tryptophan is used as control agent of pellagra.