PRODUCTION AND PARTIAL CHARACTERIZATION OF AN ENDOPOLYGALACTURONASE FROM SACCHAROMYCES-CEREVISIAE

Saccharomyces cerevisiae CECT1389 secreted an extracellular endopolyga lacturonase (EC 3.2.1.15) when grown in shake flasks in medium contain ing galactose alone, or either galactose and polygalacturonic acid or galactose and galacturonic acid as the carbon sources. The synthesis o f the enzyme was repressed by glucose and by high oxygen tensions. The enzyme was partially purified by gel exclusion chromatography over Se phacryl S-200, where it showed an apparent molecular mass of 39 kDa; t he value determined by high-performance liquid chromatography (HPLC) w as 65 kDa. The optimal temperature and pH for enzyme activity were 45 degrees C and 5.5, respectively. The K-m and V-max values for polygala cturonic acid were 4.7 mg.mL(-1) and 6.4 nmol. mL(-1).min(-1). The K-i for HgCl2 was 6.8 x 10(-5) M. The enzyme exhibited an endo-splitting mechanism as deduced from viscosimetry experiments as well as from an HPLC study of the end products.