Abstract
The glycogen phosphorylase of Dictyostelium discoideum has been purified over 200-fold from cells in the culmination stage of development. Analytical gel electrophoresis of the purified enzyme indicates one major protein band with a molecular weight of approximately 210,000. Gel elution verified the presence of phosphorylase activity associated with the protein band. Electrophoresis of partially purified extracts prepared from amoebae cells revealed the absence of phosphorylase protein. Sodium dodecyl sulfate electrophoresis on 6% gels indicated that the purified phosphorylase is composed of subunits, 95,000 in molecular weight. The purified enzyme exhibited normal Michaelis-Menten kinetics and activity was not stimulated by added nucleotides such as 5'-AMP. Nucleotide sugars (GDP-glucose, UDP-glucose, ADP-glucose) were competitive inhibitors of the phosphorylase reaction.
Highlights
Research Institute, Boston, The glycogen phosphorylase of Dictyostelium discoideum has been purified over 200-fold from cells in the culmination stage of development
Evidence suggests that the polysaccharide end products which accumulate during differentiation are derived primarily from soluble glycogen present in the amoebae prior to starvation [1, 2]
The enzyme, glycogen phosphorylase (a-1,4-glucan phosphate glucosyltransferase, EC 2.4.1.1) is present early in the developmental cycle of D. discoideum and presumably is primarily responsible for the degradation of soluble glycogen. This enzyme plays a central role in the development of the slime mold as it controls the flux of glucose units into the pathways leading to the accumulation of polysaccharide end products [4, 5]
Summary
Research Institute, Boston, The glycogen phosphorylase of Dictyostelium discoideum has been purified over 200-fold from cells in the culmination stage of development. The enzyme, glycogen phosphorylase (a-1,4-glucan phosphate glucosyltransferase, EC 2.4.1.1) is present early in the developmental cycle of D. discoideum and presumably is primarily responsible for the degradation of soluble glycogen. This enzyme plays a central role in the development of the slime mold as it controls the flux of glucose units into the pathways leading to the accumulation of polysaccharide end products (trehalose, cellulose.glycogen cell wall complex, and mucopolysaccharide) [4, 5]. As differentiation proceeds from aggregation to culmination the rate of glycogen turnover in uiuo increases about d-fold [6]. A preliminary report of these studies has been presented [9]
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