RESUMEN
Chorismic acid is a mid-metabolite that plays a central role in the metablism process distributing in the bacterium, epiphyte and plants. It is a common precursor substance of the all aromatic amino acids that can turn into phenylalanine and tyrosine catalyzed by bi-functional enzyme chorismate mutase (CM)-prephenate dehydratase (PDT) and chorismate mutase-prephenate dehydrogenase (PDH) respectively. CMp-PDT with its regulate domain Rp were called P-protein and CMt-PDH with its regulate domain Rt were called T-protein. P-protein and T-protein from E. coli. have a similar structure, both of which contained three domains: CMp, PDT, Rp in P-protein and CMt, PDH, Rt in T-protein. P-protein and T-protein are regulated by their effectors phenylalanine and tyrosine respectively through binding to their Rp and Rt domains. Rp and Rt domains were switched between P-protein and T-protein by cloning of chimeric proteins. The results showed that regulatory effects were switched along the switch of R domains and the switch of the regulatory domains lead to the switch of effectors. It means that the combination of the regulatory domain and the effector is specific and the regulating of the regulatory domain to the enzyme activity is non-specific. This property of R domains may make them possible molecular elements in the study of molecular machines.