Core oligosaccharide (or Core-OS) is a short chain of sugar residues within Gram-negative lipopolysaccharide (LPS). Core-OS are highly diverse among bacterial species and even within strains of species [1]
Core oligosaccharide (or Core-OS) is a short chain of sugar residues within Gram-negative lipopolysaccharide (LPS). Core-OS are highly diverse among bacterial species and even within strains of species [1]
The core domain always contains an oligosaccharide component which attaches directly to lipid A and commonly contains sugars such as heptose and 3-deoxy-D-mannooctulosonic acid (also known as KDO or keto-deoxyoctulosonate). [2] The LPS Cores of many bacteria also contain non-carbohydrate components, such as phosphate, amino acids, and ethanolamine substituents.
Many core structures have been described in the literature, this description is based on the traditional general structure (as found in enteric bacteria and Pseudomonas ). See the figure above for an overview of the structure found in E. coli R1.
The "base" of the inner core is 1–3 KDO residues. The last KDO is often modified with a phosphate or ethanolamine group. From the KDOs, there are attached 2–3 heptoses (i.e. L-glycero-D-mannoheptulose) that are usually phosphorylated. These KDO and heptoses comprise the "inner core". The ketosidic bond between KDO and lipid A (α2→6) is especially susceptible to acid cleavage. LPS researchers use a weak acid treatment to separate the lipid and polysaccharide portions of LPS.
An LPS molecule that includes only a lipid A and an inner core (or less. See example) is referred to as "deep-rough LPS".
The outer core is made of hexose residues that are attached to the last heptose residue in the inner core. Hexoses often found in the outer core include: D-glucose, D-mannose, D-galactose, etc.. There are usually at least three hexoses bound β1→3, with the O antigen being ligated to the third hexose. Other hexose are often found attached to the outer core, branching from the main oligomer.
LPS that include lipid A and a complete core oligosaccharide (inner and outer) is referred to as "rough LPS."
The enzymes involved in core oligosaccharide synthesis are conserved among Escherichia coli and Salmonella . Pseudomonas aeruginosa has some unique enzymes. [3] : 273
The mechanism whereby the core oligosaccharide of lipopolysaccharide affect the membrane behavior is not well understood.
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.
Mannose is a sugar monomer of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several congenital disorders of glycosylation are associated with mutations in enzymes involved in mannose metabolism.
Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide composed of O-antigen, outer core and inner core joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria. The term lipooligosaccharide ("LOS") is used to refer to a low-molecular-weight form of bacterial lipopolysaccharides.
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The bacterial outer membrane is found in gram-negative bacteria. Its composition is distinct from that of the inner cytoplasmic cell membrane - among other things, the outer leaflet of the outer membrane of many gram-negative bacteria includes a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and in some bacteria such as E. coli it is linked to the cell's peptidoglycan by Braun's lipoprotein.
Virulence factors are cellular structures, molecules and regulatory systems that enable microbial pathogens to achieve the following:
Colitose is a mannose-derived 3,6-dideoxysugar produced by certain bacteria. It is a constituent of the lipopolysaccharide.
Pantothenate kinase (EC 2.7.1.33, PanK; CoaA) is the first enzyme in the Coenzyme A (CoA) biosynthetic pathway. It phosphorylates pantothenate (vitamin B5) to form 4'-phosphopantothenate at the expense of a molecule of adenosine triphosphate (ATP). It is the rate-limiting step in the biosynthesis of CoA.
Saccharolipids are chemical compounds containing fatty acids linked directly to a sugar backbone, forming structures that are compatible with membrane bilayers. In the saccharolipids, a monosaccharide substitutes for the glycerol backbone present in glycerolipids and glycerophospholipids. The most familiar saccharolipids are the acylated glucosamine precursors of the lipid A component of the lipopolysaccharides in Gram-negative bacteria. Typical lipid A molecules are disaccharides of glucosamine, which are derivatized with as many as seven fatty-acyl chains. The minimal lipopolysaccharide required for growth in Escherichia coli is Kdo2-Lipid A, a hexa-acylated disaccharide of glucosamine (LipidA) that is glycosylated with two 3-deoxy-D-manno-octulosonic acid (Kdo) residues.
In molecular biology, the lipopolysaccharide kinase (Kdo/WaaP) family is a family of kinases.
3-Deoxy-D-arabinoheptulosonate 7-phosphate (DAHP) synthase is the first enzyme in a series of metabolic reactions known as the shikimate pathway, which is responsible for the biosynthesis of the amino acids phenylalanine, tyrosine, and tryptophan. Since it is the first enzyme in the shikimate pathway, it controls the amount of carbon entering the pathway. Enzyme inhibition is the primary method of regulating the amount of carbon entering the pathway. Forms of this enzyme differ between organisms, but can be considered DAHP synthase based upon the reaction that is catalyzed by this enzyme.
Lipid IVA 4-amino-4-deoxy-L-arabinosyltransferase is an enzyme with systematic name 4-amino-4-deoxy-alpha-L-arabinopyranosyl ditrans, octacis-undecaprenyl phosphate:lipid IVA 4-amino-4-deoxy-L-arabinopyranosyltransferase. This enzyme catalyses the following chemical reaction
Lipid IVA 3-deoxy-D-manno-octulosonic acid transferase is an enzyme with systematic name CMP-3-deoxy-D-manno-oct-2-ulosonate:lipid IVA 3-deoxy-D-manno-oct-2-ulosonate transferase. This enzyme catalyses the following chemical reaction
(KDO)-lipid IVA 3-deoxy-D-manno-octulosonic acid transferase is an enzyme with systematic name CMP-3-deoxy-D-manno-oct-2-ulosonate:(KDO)-lipid IVA 3-deoxy-D-manno-oct-2-ulosonate transferase. This enzyme catalyses the following chemical reaction
(KDO)3-lipid IVA (2-4) 3-deoxy-D-manno-octulosonic acid transferase is an enzyme with systematic name CMP-3-deoxy-D-manno-oct-2-ulosonate:(KDO)3-lipid IVA 3-deoxy-D-manno-oct-2-ulosonate transferase . This enzyme catalyses the following chemical reaction
3-deoxy-D-manno-octulosonic acid kinase is an enzyme with systematic name ATP:(KDO)-lipid IVA 3-deoxy-alpha-D-manno-oct-2-ulopyranose 4-phosphotransferase. This enzyme catalyses the following chemical reaction
The multidrug/oligosaccharidyl-lipid/polysaccharide (MOP) flippase superfamily is a group of integral membrane protein families. The MOP flippase superfamily includes twelve distantly related families, six for which functional data are available:
N-glycosyltransferase is an enzyme in prokaryotes which transfers individual hexoses onto asparagine sidechains in substrate proteins, using a nucleotide-bound intermediary, within the cytoplasm. They are distinct from regular N-glycosylating enzymes, which are oligosaccharyltransferases that transfer pre-assembled oligosaccharides. Both enzyme families however target a shared amino acid sequence asparagine—-any amino acid except proline—serine or threonine (N–x–S/T), with some variations.
The Phosphate (Pho) regulon is a regulatory mechanism used for the conservation and management of inorganic phosphate within the cell. It was first discovered in Escherichia coli as an operating system for the bacterial strain, and was later identified in other species. The Pho system is composed of various components including extracellular enzymes and transporters that are capable of phosphate assimilation in addition to extracting inorganic phosphate from organic sources. This is an essential process since phosphate plays an important role in cellular membranes, genetic expression, and metabolism within the cell. Under low nutrient availability, the Pho regulon helps the cell survive and thrive despite a depletion of phosphate within the environment. When this occurs, phosphate starvation-inducible (psi) genes activate other proteins that aid in the transport of inorganic phosphate.