A thioredoxin-activated fructose-1,6-bisphosphatase from the cyanobacterium Synechococcus 6301

Fructose-1,6-bisphosphatase was isolated from the cyanobacterium Synechococcus 6301 by acid precipitation, ammonium-sulfate fractionation, and Sephadex gel chromatography. The purified enzyme needed thiols and MgCl₂ for activity. The following K_m-values were obtained: a) for fructose-1,6-bisphosphate: 1.7 mM; b) for MgCl₂: 12.5 mM; c) for dithiocrythritol: 0,56 mM; d) for glutathione: 14 mM; e) for mercaptoethanol: 22 mM; f) for cysteine: 50 mM. Thioredoxin B isolated from this organism will activate this fructose-1,6-bisphosphatase. The K_m of thioredoxin B for this fructose-1,6-bisphosphatase was determined to be 1.7 M, endicotiy that thioredoxin might activate the fructose-1,6-bisphosphatase in Synechococcus in vivo.