The Regulative Properties of UDPglucose: d‐Fructose‐6‐phosphate 2‐Glucosyltransferase (Sucrose Phosphate Synthetase) from Vicia faba Cotyledons

摘要: Sucrose phosphate synthetase of cotyledons Vicia faba was purified about 130-fold by means ammonium sulfate and protamine fractionation. After freezing thawing an activator could be separated centrifugation from the enzyme. The regulatory properties activator-bound activator-devoid enzyme were compared. Under normal conditions assay had scarcely any activity, but activated citrate, a number dicarboxylic acids protamin. saturation curves these effectors sigmoidal. Also substrate sigmoid shaped in absence presence converted them to hyperbolic form. Quite different effect citrate on activity enzyme: at low concentration it inhibited production sucrose-6-phosphate. At 10–20 mM minimum measured. higher concentrations reactivation occurred. This preparation further inhibited, not reactivated, UDP, UTP, ATP, ADP other phosphates which influence Experiences where investigated UTP-inhibited suggest that both share binding sites. The role control activities sucrose (activation) phosphofructokinase (inhibition), enzymes competing for branchpoint metabolite fructose-6-phosphate, is discussed.