Article

Crystal structure of glycogen synthase: Homologous enzymes catalyze glycogen synthesis and degradation

Unité de Biochimie Structurale, URA 2185 CNRS, Institut Pasteur, Paris, France.
The EMBO Journal (Impact Factor: 10.43). 09/2004; 23(16):3196-205. DOI: 10.1038/sj.emboj.7600324
Source: PubMed

ABSTRACT

Glycogen and starch are the major readily accessible energy storage compounds in nearly all living organisms. Glycogen is a very large branched glucose homopolymer containing about 90% alpha-1,4-glucosidic linkages and 10% alpha-1,6 linkages. Its synthesis and degradation constitute central pathways in the metabolism of living cells regulating a global carbon/energy buffer compartment. Glycogen biosynthesis involves the action of several enzymes among which glycogen synthase catalyzes the synthesis of the alpha-1,4-glucose backbone. We now report the first crystal structure of glycogen synthase in the presence and absence of adenosine diphosphate. The overall fold and the active site architecture of the protein are remarkably similar to those of glycogen phosphorylase, indicating a common catalytic mechanism and comparable substrate-binding properties. In contrast to glycogen phosphorylase, glycogen synthase has a much wider catalytic cleft, which is predicted to undergo an important interdomain 'closure' movement during the catalytic cycle. The structures also provide useful hints to shed light on the allosteric regulation mechanisms of yeast/mammalian glycogen synthases.

Download full-text

Full-text

Available from: William Shepard
    • "Based on comparative structural analysis of AtSus1 in closed conformation and N. europaea SuSy in open conformation an open/close induced fit mechanism was suggested. This is in good agreement with similar large conformational changes in other retaining GT-B GTs (Buschiazzo et al., 2004;Sheng et al., 2009). Family GT-4 comprises a wide variety of GTs, including SuSy, sucrose phosphate synthase, trehalose synthase, trehalose phosphorylase, and many others, which are characterized by broad acceptor and donorsubstrate specificities. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Sucrose synthase (SuSy, EC 2.4.1.13) is a glycosyltransferase (GT) long known from plants and more recently discovered in bacteria. The enzyme catalyzes the reversible transfer of a glucosyl moiety between fructose and a nucleoside diphosphate (NDP) (sucrose+NDP↔NDP-glucose+fructose). The equilibrium for sucrose conversion is pH dependent, and pH values between 5.5 and 7.5 promote NDP-glucose formation. The conversion of a bulk chemical to high-priced NDP-glucose in a one-step reaction provides the key aspect for industrial interest. NDP-sugars are important as such and as key intermediates for glycosylation reactions by highly selective Leloir GTs. SuSy has gained renewed interest as industrially attractive biocatalyst, due to substantial scientific progresses achieved in the last few years. These include biochemical characterization of bacterial SuSys, overproduction of recombinant SuSys, structural information useful for design of tailor-made catalysts, and development of one-pot SuSy-GT cascade reactions for production of several relevant glycosides. These advances could pave the way for the application of Leloir GTs to be used in cost-effective processes. This review provides a framework for application requirements, focusing on catalytic properties, heterologous enzyme production and reaction engineering. The potential of SuSy biocatalysis will be presented based on various biotechnological applications: NDP-sugar synthesis; sucrose analog synthesis; glycoside synthesis by SuSy-GT cascade reactions.
    No preview · Article · Dec 2015 · Biotechnology advances
  • Source
    • "Interestingly, abundant POV-encoded PPP enzymes (for example, gnd, transketolase (tkt), and talC) (see Additional file 6: Table S4) represent all three enzymes whose metabolic flux is increased in starved E. coli[43]. Moreover, the glycogen biosynthetic gene (glgA), present in all viromes suggests that some viral infections trigger a starvation response in their hosts to redistribute carbon through non-glycolytic pathways [44,45]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Marine ecosystem function is largely determined by matter and energy transformations mediated by microbial community interaction networks. Viral infection modulates network properties through mortality, gene transfer and metabolic reprogramming. Here we explore the nature and extent of viral metabolic reprogramming throughout the Pacific Ocean depth continuum. We describe 35 marine viral gene families with potential to reprogram metabolic flux through central metabolic pathways recovered from Pacific Ocean waters. Four of these families have been previously reported but 31 are novel. These known and new carbon pathway auxiliary metabolic genes were recovered from a total of 22 viral metagenomes in which viral auxiliary metabolic genes were differentiated from low-level cellular DNA inputs based on small subunit ribosomal RNA gene content, taxonomy, fragment recruitment and genomic context information. Auxiliary metabolic gene distribution patterns reveal that marine viruses target overlapping, but relatively distinct pathways in sunlit and dark ocean waters to redirect host carbon flux towards energy production and viral genome replication under low nutrient, niche-differentiated conditions throughout the depth continuum. Given half of ocean microbes are infected by viruses at any given time, these findings of broad viral metabolic reprogramming suggest the need for renewed consideration of viruses in global ocean carbon models.
    Full-text · Article · Nov 2013 · Genome biology
  • Source
    • "We further demonstrated that the interaction between two regions within the SBDs (D(385e413) in D2 and D(564e604) in D3) and the CD, as well as the full starch binding capacity of the D2 domain are requisites for the full catalytic activity of SSIII [11] [20]. Besides the biochemical characterization, we had proposed a structural model of SSIII-CD that predicts a global structural similarity with the GS from Agrobacterium tumefaciens [21] [22]. Particularly , a fully conservation of the ADP-binding residues was found: residues participating in the binding of ADPGlc are evolutionary conserved in plants and algae [22]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Glycogen and starch, the major storage carbohydrate in most living organisms, result mainly from the action of starch or glycogen synthases (SS or GS, respectively, EC 2.4.1.21). SSIII from Arabidopsis thaliana is an SS isoform with a particular modular organization: the C-terminal highly conserved glycosyltransferase domain is preceded by a unique specific region (SSIII-SD) which contains three in tandem starch binding domains (SBDs, named D1, D2 and D3) characteristic of polysaccharide degrading enzymes. N-terminal SBDs have a probed regulatory role in SSIII activity, showing starch binding ability and modulating the catalytic properties of the enzyme. On the other hand, GS from Agrobacterium tumefaciens has a simple primary structure organization, characterized only by the highly conserved glycosyltransferase domain and lacking SBDs. To further investigate the functional role of A. thaliana SSIII-SD, three chimeric proteins were constructed combining the SBDs from A. thaliana with the GS from A. tumefaciens. Recombinant proteins were expressed in and purified to homogeneity from Escherichia coli cells in order to be kinetically characterized. Furthermore, we tested the ability to restore in vivo glycogen biosynthesis in transformed E. coli glgA(-) cells, deficient in GS. Results show that the D3-GS chimeric enzyme showed increased capacity of glycogen synthesis in vivo with minor changes in its kinetics parameters compared to GS.
    Full-text · Article · Jun 2013 · Biochimie
Show more