Comparative studies on the properties of glycogen phosphorylases from the foot muscles of two benthic bivalves, Sunetta scripta and Villorita cyprenoides, having different habitats.

Glycogen phosphorylase (1,4-alpha-D-glucan:orthophosphate-alpha-D-glucosyl transferase, EC 2.4.1.1) was partially purified from two bivalves found in different habitats, viz. Villorita cyprenoides, an estuarine bivalve, and Sunetta scripta, a marine bivalve, and their properties compared with other animal phosphorylases. While the kinetic mechanism was same as that of phosphorylases from other animal sources, it differed in the control mechanism from other phosphorylases. The observed differences support the earlier finding that the control mechanism adopted by different animals is dependent on the evolutionary status and energy needs.

Predicted secondary structure of glycogen phosphorylase from Escherichia coli as deduced using Chou-Fasman analysis.

Secondary structure of glycogen phosphorylase from Escherichia coli has been deduced using Chou-Fasman analysis. Out of 809 amino acid residues, 244 residues showed formation of alpha-helix (30%), 218 residues beta-pleated sheet (27%) and 192 residues (24%) showed formation of reverse beta turn, distributed all over the sequence. There are total 27 alpha-helix and 31 beta-pleated sheets distributed all over the molecule. A structure consisting of three consecutive strands of beta-pleated sheets and two joining alpha-helix is predicted for the stretch of the primary sequence from residues 325 to 372, thus showing the presence of a Rossman fold super secondary structure. There is a tyrosine at position 350 in the super secondary structure, in the area to contain a reverse beta turn. Several amino acids pairs are present in the sequence having Rossman fold super secondary structure.