Abstract
Baker's or brewer's yeast pyruvate decarboxylase (EC 4.1.1.1) was purified and separated from the cofactors according to the procedures of Ullrich, Wittof, Gubler^<4)> and Morey, Juni.^<6)> Both of enzymes showed maximum activities at pH 6.2 in the presence of TPP and divalent metal ions. Baker's yeast apo-pyruvate decarboxylase was activated by Mn^<2+>, Mg^<2+>, Ca^<2+>, in the ratios of 4 : 2 : 1 while brewer's yeast apoenzyme was in those of 9 : 3 : 1. Mg^<2+>, Ca^<2+> bound to 1 mole of enzyme was found to be about 0.8 moles. The activities of 1 mole enzyme was almost completely lost in the presence of 2 or 5 moles of PCMB or BrCN respectively and approximately 40% of its activities was lost with 5 moles of DTNB. The formation of CO_2,CH_3CHO and acetoin were all inhibited with PCMB to the same extent and the interaction between enzyme bound TPP and PCMB seems to be responsible for the above inhibitions.
