Aromatic amino acids are essential for the growth and maintenance of animals, but these amino acids are not synthesized ina nimal because of the lack of the Shikimate pathway. However, plants and micro organisms possess this pathway and are able to synthesize these amino acids and other secondary metabolites necessary for the everyday activities of animals.

Even though it is absent in animal, the shikimate pathway is important for animal because

1) It is a source of essential aromatic amino acids such as phenylalanie, Tyrosine and Tryptophan

2.) Its product(s) are presursors to the biosynthesis of active neuroactive substances such dopamine, epinephrine and norepinephrine (the catecholamines) as well as serotonin (5-Hydroxyltryptamine)

3) the product of the pathway is the precursor of the biosynthesis of secondary metabolites such as alkaloids (in plants) and antibiotics (in microbes, which are therapeutically important to animals.

Absence of shikimate pathway in humans also gives an opportunity to target enzymes involved in shikimate pathway in pathogens for drugs.

As mentioned above, Skikimic pathway is absent in human & animals and that's why 3 amino acids (phenylaalanine, tryptophan, and conditinally tyrosine)  are essential to be  obtained from plant/microbial sources. interestingly,  intestial microflora of animals are equipped with this pathway to provide these esential nutrients to some extent. Other importance of this biochecal pathway is nicely depicted by Ms. Folarin D. thanks all