X-ray structure of pyruvate formate-lyase in complex with pyruvate and CoA. How the enzyme uses the Cys-418 thiyl radical for pyruvate cleavage.

The glycyl radical enzyme pyruvate formate-lyase (PFL) synthesizes acetyl-CoA and formate from pyruvate and CoA. With the crystal structure of the non-radical form of PFL in complex with its two substrates, we have trapped the moment prior to pyruvate cleavage. The structure reveals how the active site aligns the scissile bond of pyruvate for radical attack, prevents non-radical side reactions of the pyruvate, and confines radical migration. The structure shows CoA in a syn conformation awaiting pyruvate cleavage. By changing to an anti conformation, without affecting the adenine binding mode of CoA, the thiol of CoA could pick up the acetyl group resulting from pyruvate cleavage.