Details of the shikimic acid pathway, I

This figure depicts the initial unbranched pathway from erythrose-4-phosphate and PEP to chorismic acid.

The first reaction is driven by loss of phosphate from PEP.

In the second reaction an unusual cobalt-requiring enzyme effects ring closure with dehydrogenation and loss of the second phosphate.

Dehydration in the third step yields dehydroshikimate, which is then reduced by NADPH to shikimate.

A three-carbon side chain is then attached via phosphorylation of shikimate and reaction with a second molecule of PEP.

Dephosphorylation of this intermediate gives chorismate, the branch point of the pathway.