A protein-glucan intermediate during paramylon synthesis

Tomos, A. D.; Northcote, D. H.

doi:10.1042/bj1740283

Cited by 37 publications

(16 citation statements)

References 22 publications

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“…Paramylon is synthesized by membranebound paramylon synthases (UDP-glucose:β-1,3-glucan β-glucosyltransferase), that preferentially uses UDP-glucose (but not ADPglucose) as the glucose donor (Marechal and Goldemberg 1964;Tomos and Northcote 1978). A recent comprehensive gene expression analysis of Euglena identified two probable paramylon synthases, which have 14 and 19 membrane spanning domains (Yoshida et al 2016).…”

Section: Degradation Of Paramylonmentioning

confidence: 99%

Wax Ester Fermentation and Its Application for Biofuel Production

Inui

Ishikawa

Tamoi

2017

Advances in Experimental Medicine and Biology

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In Euglena cells under anaerobic conditions, paramylon, the storage polysaccharide, is promptly degraded and converted to wax esters. The wax esters synthesized are composed of saturated fatty acids and alcohols with chain lengths of 10-18, and the major constituents are myristic acid and myristyl alcohol. Since the anaerobic cells gain ATP through the conversion of paramylon to wax esters, the phenomenon is named "wax ester fermentation". The wax ester fermentation is quite unique in that the end products, i.e. wax esters, have relatively high molecular weights, are insoluble in water, and accumulate in the cells, in contrast to the common fermentation end products such as lactic acid and ethanol.A unique metabolic pathway involved in the wax ester fermentation is the mitochondrial fatty acid synthetic system. In this system, fatty acid are synthesized by the reversal of β-oxidation with an exception that trans-2-enoyl-CoA reductase functions instead of acyl-CoA dehydrogenase. Therefore, acetyl-CoA is directly used as a C donor in this fatty acid synthesis, and the conversion of acetyl-CoA to malonyl-CoA, which requires ATP, is not necessary. Consequently, the mitochondrial fatty acid synthetic system makes possible the net gain of ATP through the synthesis of wax esters from paramylon. In addition, acetyl-CoA is provided in the anaerobic cells from pyruvate by the action of a unique enzyme, oxygen sensitive pyruvate:NADP oxidoreductase, instead of the common pyruvate dehydrogenase multienzyme complex.Wax esters produced by anaerobic Euglena are promising biofuels because myristic acid (C) in contrast to other algal produced fatty acids, such as palmitic acid (C) and stearic acid (C), has a low freezing point making it suitable as a drop-in jet fuel. To improve wax ester production, the molecular mechanisms by which wax ester fermentation is regulated in response to aerobic and anaerobic conditions have been gradually elucidated by identifying individual genes related to the wax ester fermentation metabolic pathway and by comprehensive gene/protein expression analysis. In addition, expression of the cyanobacterial Calvin cycle fructose-1,6-bisphosphatase/sedohepturose-1,7-bisphosphatase, in Euglena provided photosynthesis resulting in increased paramylon accumulation enhancing wax ester production. This chapter will discuss the biochemistry of the wax ester fermentation, recent advances in our understanding of the regulation of the wax ester fermentation and genetic engineering approaches to increase production of wax esters for biofuels.

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Section: Degradation Of Paramylonmentioning

confidence: 99%

Wax Ester Fermentation and Its Application for Biofuel Production

Inui

Ishikawa

Tamoi

2017

Advances in Experimental Medicine and Biology

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“…It must be stressed that "-1,3-linked storage "-glucans are widely distributed in the bikont branch of the eukaryotes (Fig. 4.1, see legend for definition of bikont) and that very few reports address the biochemistry of their synthesis or mobilization (Bäumer et al 2001;Goldemberg and Marechal 1963;Tomos and Northcote 1978;Vogel and Barber 1968). Most soluble "-glucan forms, such as laminarin, chrysolaminarin, and mycolaminarin, contain, in addition, "-1,6 branches, while the very highly crystalline paramylon found in Euglena (an excavate unicellular green alga) and Traditionally the eukaryotes are divided into the unikonts and bikonts which were previously thought to contain only uniflagellated cells or biflagellated cells.…”

Section: The Bacterial Eukaryote and Archeal Domainsmentioning

confidence: 99%

The Transition from Glycogen to Starch Metabolism in Cyanobacteria and Eukaryotes

Ball

Colleoni

Arias

2015

Starch

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'-1,4-linked glucan chains branched through '-1,6 glucosidic lineages define the most frequently found storage polysaccharides in living cells. These glucans come in two very distinct forms known as glycogen and starch. The small water-soluble glycogen particles distribute widely in Archaea, Bacteria, and heterotrophic eukaryotes, while semicrystalline solid starch seems to be restricted to photosynthetic eukaryotes. This review focusses on the so-called glycosylnucleotide-dependent pathway of starch and glycogen synthesis. Through comparative biochemistry of storage polysaccharide metabolism in distinct clades, we will review the evidence sustaining that starch has evolved from preexisting glycogen metabolism several times during the evolution of photosynthetic eukaryotes and cyanobacteria. This review will also describe the possible function of storage polysaccharide metabolism in establishing metabolic symbiosis during plastid endosymbiosis. We will detail the evidence sustaining that storage polysaccharide metabolism was used by three distinct organisms to establish a tripartite symbiosis that facilitated metabolic integration of free-living cyanobacteria into evolving organelles.

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“…The enzyme, which is associated with particles, was highly specific for the donor substrate, since ADPG, TDPG, and UDP-f3-D-glucose were inactive, and apparently did not require an external primer. This latter aspect has been examined by TOMOS and NORTHCOTE (1978) who concluded that paramylon was, in fact, synthesized on to a protein rather than carbohydrate primer. The bond linking the glucan to the protein was tentatively identified as a pyrophosphate linkage.…”

Section: The Metabolism Of Paramylonmentioning

confidence: 97%