Molybdenum reductase in Enterobacter cloacae

Under anaerobic conditions in glucose-yeast extract medium with phosphate, Enterobacter cloacae strain 48 grew well and reduced Mo6+, to Mo5+. The activity of Mo6+-reductase was measured by the formation of molybdenum blue (complexation between Mo5+ and phosphate ion). Models based on logistic and Luedeking-Piret equations were found adequate to describe the growth of E. and Mo6+-reductase cloacae production. Mo6+-reductase production was found to be a growth-associated process. Washed intact cells, membrane fraction (after disruption using a sonicator) and fluid supernatant (after cell disruption) were able to reduce Mo6+. However, Mo6+-reductase activity was much lower in the supernatant fluid. The (NH4)(2)SO4-precipitated Mo6+-reductase extract from fluid supernatant was assayed for its properties. The optimum pH and temperature for Mo6+-reductase activity were 8 and 30 degrees C, respectively. The apparent Michaelis-Menten constant (K-m) and a maximum velocity (V-max) were 16.5 mM and 0.0192 mu mol/ml.h, respectively.