- Identification of D-proline reductase from Clostridium sticklandii as a selenoenzyme and indications for a catalytically active pyruvoyl group derived from a cysteine residue by cleavage of a proprotein. Kabisch, U.C., Gräntzdörffer, A., Schierhorn, A., Rücknagel, K.P., Andreesen, J.R., Pich, A. J. Biol. Chem. (1999)