PURIFICATION AND THE EFFECT OF MANGANESE IONS ON THE ACTIVITY OF CARBOXYMETHYLCELLULASES FROM ASPERGILLUS-NIGER AND CELLULOMONAS-BIAZOTEA

Carboxymethylcellulases (CMCases) from Aspergillus niger and Cellulomo nas biazotea were purified by a combination of ammonium sulfate precip itation, anion-exchange and gel-filtration chromatography with a 12- a nd 9-fold increase in the purification factor. The native and subunit molar mass of CMCase from A. niger were 40 and 25-57 kDa, respectively , while those from C. biazotea were 23 and 20-30 kDa, respectively. Lo w concentrations of Mn2+ activated the enzymes from both organisms (mi xed activation) with apparent activation constants of 0.80 and 0.45 mm ol/L of CMCases from A. niger and C. biazotea, respectively, while at higher CMC concentrations Mn2+ inhibited the enzymes (mixed and partia l uncompetitive inhibition). The reason for this complex behavior is t hat more than one Mn2+ bind to the same enzyme form with the apparent average inhibition constants of 2.7 and 1.3 mmol/L for CMCases from A. niger and C. biazotea, respectively.