Adenylosuccinate synthase from Saccharomyces cerevisiae: homologous overexpression, purification and characterization of the recombinant protein

Adenylosuccinate synthase (EC 6.3.4.4) catalyses the first committed step i n the synthesis of adenosine. We have overexpressed the cloned gene of Sacc haromyces cerevisiae (ADE12) in S. cerevisiae. The recombinant enzyme exhib its similar kinetic behaviour to that of the native enzyme purified from S. cerevisiae. This ter-reactant dimeric enzyme shows Michaelis-Menten kineti cs only with IMP. L-Aspartate and GTP display a weak negative co-operativit y (Hill coefficient 0.8-0.9). This negative co-operativity has not yet been reported for adenylosuccinate synthases from other organisms. Another unus ual feature of the enzyme from S. cerevisiae is its negligible inhibition b y adenine nucleotides and its pronounced inhibition by Cl- ions.