Deaminates also threonine, particularly when it is present in high concentration. L-serine = NH4(+) + pyruvate Binds 1 [4Fe-4S] cluster. Carbohydrate biosynthesis; gluconeogenesis. It is made aerobically and anaerobically, in minimal medium. Activated by post-translational modification by a system involving at least three gene products. Activation is mimicked in vitro by iron and dithiothreitol. There is considerable evidence for a free-radical activation mechanism. Belongs to the iron-sulfur dependent L-serine dehydratase family.