Partial purification of an iron-dependent L-serine dehydratase from Clostridium sticklandii

An oxygen-sensitive and highly unstable L -serine dehydratase was partially purified from the Grampositive anaerobe Clostridium sticklandii. The final active preparation contained five proteins of 27, 30, 44.5, 46, and 58 kDa as judged by SDS-PAGE. The N-terminal sequence of the 30 kDa subunit showed some similarity to the α-subunits of the iron-containing L -serine dehydratases from Clostridium propionicum and Peptostreptococcus asaccharolyticus. Oxygen-inactivated L -serine dehydratase from C. sticklandii was reactivated by incubation with Fe²⁺ under reducing conditions. Furthermore, the enzyme was inactivated by iron-chelating substances like phenanthroline and EDTA. Pyridoxal-5-phosphate (PLP) did not stimulate the activity, and known inhibitors of PLP-containing enzymes such as NaBH₄ had no effect on the activity of L -serine dehydratase from C. sticklandii.