Escherichiá coli polyglucose phosphorylases

Abstract

Escherichia coli, K-12, possesses two distinct polyglucose (oligoglucoside) phosphorylases (α-1,4-glucan: orthophosphate glucosyltransferase, E.C. 2.4.1.1). The two enzymes may be separated by ammonium sulfate fractionation or by DEAE-cellulose column chromatography. One of the enzymes is a maltodextrin phosphorylase. This enzyme is present in glucose-grown cells but is induced to a 10-fold higher level in maltose-grown cells. The maltodextrin phosphorylase shows a decided preference for short chain dextrins over glycogen as the polyglucose acceptor. The second enzyme is a constitutive glycogen phosphorylase. The level of the glycogen phosphorylase is independent of the carbon source used for growth. The glycogen phosphorylase shows higher activity with glycogen than with dextrin. The maltodextrin phosphorylase is much more heat stable than the glycogen phosphorylase. Both enzymes are stimulated slightly by AMP and strongly inhibited by heavy metals and pCMB. The glycogen phosphorylase shows a 4-fold activation by NaF and a 10-fold activation by Na 2SO 4. Sulfate activation is sigmoidal. The maltodextrin phosphorylase shows little or no salt activation.