3-[N-morpholino]-propanesulfonic acid (MOPS),tris[hydroxymethyl]-aminomethane (TRIS), 2-[N-morpholino]-ethanesulfonic acid (MES), and dithiothreitol (DTT) were supplied by Sigma Chemical Company (St. Louis,MO, USA). Thiamin pyrophosphate (TPP) and coenzymes were purchased from Boehringer (Mannheim, Germany).