Iron-sulfur clusters as alternatives to pyridoxal-5′-phosphate in bacterial L-serine dehydratases: Cloning of the gene encoding the β-subunit of the enzyme from Peptostreptococcus asaccharolyticus

Abstract

L-Serine dehydratases from the strictly anaerobic bacteria Peptostreptococcus asaccharolyticus and Clostridium propionicum were shown to contain [4Fe-4S]clusters but no pyridoxal-5′-phosphate. Both enzymes are inactivated by oxygen and reactivated by ferrous ion under anaerobic conditions. In combination with EPR-studies, the data indicate an aconitase-like mechanism of the dehydration of L-serine. Both enzymes are composed of two different subunits (α, 30 kDa and β, 25 kDa). The gene coding for the β-subunit from P. asaccharolyticus was cloned and sequenced. The N-terminus of the deduced amino acid sequence shows significant identities to that of the β-subunit of C. propionicum as well as to the N-termini of both L-serine dehydratases from Escherichia coli.