Disease relevance of glgP

• The glgP gene, which codes for glycogen phosphorylase, was cloned from a genomic library of Escherichia coli [1].

High impact information on glgP

• Glycogen phosphorylase (E.C.2.4.1.1) was the first enzyme shown to be regulated by allosteric effectors and by protein phosphorylation [2].
• In this review, we compare crystallographic structures of regulated and unregulated phosphorylases, including maltodextrin phosphorylase (MalP) from Escherichia coli, glycogen phosphorylase from yeast, and mammalian isozymes from muscle and liver tissues [3].
• The overall structure of MalP shows a similar fold to GP and the catalytic sites are highly conserved [4].
• The finding that, in early exponential phase, mutant cells contain higher levels of glycogen phosphorylase a, in addition to a lower amount of total glycogen synthase activity observed in medium-late exponential phase, could account for the difference found in glycogen accumulation [5].
• The 2.0A crystal structure of the MalP/Glc1P binary complex shows that the Glc1P substrate adopts a conformation seen previously with both inactive and active forms of mammalian GP, with the phosphate group not in close contact with the 5'-phosphate group of the essential pyridoxal phosphate (PLP) cofactor [6].

Chemical compound and disease context of glgP

• Glycogen phosphorylase, the product of the glgP Gene, catalyzes glycogen breakdown by removing glucose units from the nonreducing ends in Escherichia coli [7].

Biological context of glgP

• The nucleotide sequence of the glgP gene contained a single open reading frame encoding a protein consisting of 790 amino acid residues [1].
• The location and role of the active-site arginyl residues in the beta 2 subunit and in two other enzymes which contain pyridoxal phosphate, aspartate aminotransferase and glycogen phosphorylase, are compared [8].

Anatomical context of glgP

• Moderate increases of glycogen phosphorylase activity were accompanied by marked reductions of the intracellular glycogen levels in cells cultured in the presence of glucose [7].

Associations of glgP with chemical compounds

• In the active MalP enzyme, the residue Arg569 stabilizes the negative-charged Glc1P, whereas in the inactive form of GP this key residue is held away from the catalytic site by loop 280s and an allosteric transition of the mammalian enzyme is required for activation [6].
• These results suggest that the GlgX protein is predominantly involved in glycogen catabolism by selectively debranching the polysaccharide outer chains that were previously recessed by glycogen phosphorylase [9].
• Homology between O-linked GlcNAc transferases and proteins of the glycogen phosphorylase superfamily [10].
• Here, remote homology is reported between the OGTs and a large group of diverse sugar processing enzymes, including proteins with known structure such as glycogen phosphorylase, UDP-GlcNAc 2-epimerase, and the glycosyl transferase MurG [10].

Other interactions of glgP

• The gene, glgP, is located immediately downstream from glgA, the gene for glycogen synthase [11].
• Similarly, the expression of the degradative enzyme glycogen phosphorylase, which is encoded by glgY, was found to be negatively regulated via csrA in vivo [12].
• The cloned region which follows glgA contains an incomplete ORF (1149 bp), glgY, which appears to encode 383 aa of the N terminus of glycogen phosphorylase, based upon sequence similarity with the enzyme from rabbit muscle (47% identical aa residues) and with maltodextrin phosphorylase from E. coli (37% identical aa residues) [13].

Analytical, diagnostic and therapeutic context of glgP

• Molecular cloning and sequencing of the glycogen phosphorylase gene from Escherichia coli [1].

References