Fructose-2,6-bisphosphate Activates Pyrophosphate: d-Fructose 6-Phosphate 1-Phosphotransferase from Euglena gracilis

When hexavalent chromium (Cr⁶⁺) tolerant Pseudomonas ambigua G-l was cultivated in nutrient broth containing 150 ppm Cr^{6 +}, the Cr⁶⁺ content of the broth rapidly decreased. The Cr⁶⁺ reducing enzyme found in a cell-free extract of P. ambigua G-l required NADH but not NADPH as a hydrogen donor for the reduction of Cr^{6 +}. The specific activities of cell-free extracts of several Cr⁶⁺ sensitive mutants derived from P. ambigua G-l showed decreases to one fourth to one tenth of that of P. ambigua G-l. Glucose protected the Cr⁶⁺ reducing enzyme against inac-tivation on dialysis.