BACTERIAL L-SERINE DEHYDRATASES - A NEW FAMILY OF ENZYMES CONTAINING IRON-SULFUR CLUSTERS

Two families of enzymes are described which catalyse identical chemica l reactions but differ in their prosthetic groups and hence in their m echanism of action. One family, the pyridoxal-5'-phosphate (PLP)-depen dent L-threonine dehydratases, also use L-serine as substrate. The oth er, hitherto unrecognized family is the iron-dependent, highly specifi c bacterial L-serine dehydratases. It has been shown that L-serine deh ydratase from the anaerobic bacterium Peptostreptococcus asaccharolyti cus contains an iron-sulfur cluster but no PLP. A mechanism for the de hydration of L-serine which is similar, but not identical, to that of the dehydration of citrate catalysed by aconitase is proposed.