Activation of pyruvate formate-lyase under anaerobic conditions by generation of an organic free radical, using S-adenosylmethionine and reduced flavodoxin as cosubstrates to produce 5'-deoxy-adenosine. glycyl-[formate C-acetyltransferase] + reduced [flavodoxin] + S-adenosyl-L-methionine = 5'-deoxyadenosine + glycin-2-yl radical-[formate C-acetyltransferase] + H(+) + L-methionine + semiquinone [flavodoxin] Binds 1 [4Fe-4S] cluster. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. Belongs to the organic radical-activating enzymes family.