GLUCOSE-6-PHOSPHATE DEHYDROGENASE IN CELL FREE EXTRACTS OF ZYMOMONAS MOBILIS

Glucose-6-phosphate dehydrogenase activity in cell free extracts o Zymomonas mobilis showed marked differences when compared with the corresponding enzyme of Escherichia coli. It exhibited 3 times higher activity and the reaction rate over 10 min gave linearity only up to a cell free protein concentration of 0.15 mg protein. This different behaviour was not a function of environmental growth conditions of the culture nor of the nine different assay methods employed. A constant relationship existed between the specific G-6-P dehydrogenase protein and the total protein concentration in the cell free extract. The enzyme was stable for at least 5 h at 4°C in Tris-NaCl-MgCl2-buffer. An investigation of the properties of G-6-P dehydrogenase from Z. mobilis revealed a pH optimum of 8.7 with a rapid decline towards the acidic and a small decrease towards the alkaline side. The Km values were 5×10-4m for glucose-6-phosphate and 3.6×10-5m NADP+. The addition of 1×10-2m MgCl2 produced optimal activity but higher concentrations inhibited the enzyme reaction. These results were discussed with those from other sources and found to be unique for Zymomonas mobilis. © 1968 Springer-Verlag.