Catalyzes the anti-1,4-elimination of the C-3 phosphate and the C-6 proR hydrogen from 5-enolpyruvylshikimate-3-phosphate (EPSP) to yield chorismate, which is the branch point compound that serves as the starting substrate for the three terminal pathways of aromatic amino acid biosynthesis. This reaction introduces a second double bond into the aromatic ring system. It uses NADPH to reduce FMN. 5-O-(1-carboxyvinyl)-3-phosphoshikimate = chorismate + phosphate Reduced FMN (FMNH(2)). It can also use FAD, however FMN is the preferred cofactor. Competitively inhibited by 6R-6-fluoro-EPSP. kcat is 16.5 sec(-1) for phospholyase activity with EPSP as substrate. kcat is 27 sec(-1) for phospholyase activity with EPSP as substrate. Optimum pH is between 7.5 and 8. Metabolic intermediate biosynthesis; chorismate biosynthesis; chorismate from D-erythrose 4-phosphate and phosphoenolpyruvate: step 7/7. Homotetramer. Belongs to the chorismate synthase family.