Ferrous ion-dependent L-serine dehydratase from Clostridium acidiurici

l-Serine dehydratase from Clostridium acidiurici was purified 400-fold. The enzyme required activation by catalytic amounts of ferrous ion and a thiol reducing agent before the addition of substrate. Several cations tested were unable to substitute for divalent iron. The reducing agent of choice was dithiothreitol. The activation was presumed to result in the formation of an iron-enzyme complex, because once activated the enzyme retained essentially full activity in a reaction mixture not supplemented with iron or reducing agent. The reaction with substrate was carried out at pH 8.4 in phosphate buffer and was specific for l-serine. The presence of pyridoxal phosphate as coenzyme was indicated by absorption maxima at 330 and 420 nm and fluorescence maxima at 390 and 520 nm.