Xylulose 5-phosphate

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Xylulose 5-phosphate
Xylulose 5-phosphate.svg
Names
IUPAC name
5-O-Phosphonato-D-xylulose
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
MeSH xylulose-5-phosphate
PubChem CID
  • InChI=1S/C5H11O8P/c6-1-3(7)5(9)4(8)2-13-14(10,11)12/h4-6,8-9H,1-2H2,(H2,10,11,12)/p-2/t4-,5-/m1/s1 Yes check.svgY
    Key: FNZLKVNUWIIPSJ-RFZPGFLSSA-L Yes check.svgY
  • [O-]P([O-])(=O)OC[C@@H](O)[C@H](O)C(=O)CO
Properties
C5H11O8P
Molar mass 230.109 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

D-Xylulose 5-phosphate (D-xylulose-5-P) is an intermediate in the pentose phosphate pathway. It is a ketose sugar formed from ribulose-5-phosphate by ribulose-5-phosphate epimerase. In the non-oxidative branch of the pentose phosphate pathway, xylulose-5-phosphate acts as a donor of two-carbon ketone groups in transketolase reactions. [1]

Xylulose-5-phosphate also plays a crucial role in the regulation of glycolysis through its interaction with the bifunctional enzyme PFK2/FBPase2. Specifically, it activates protein phosphatase, which then dephosphorylates PFK2/FBPase2. This inactivates the FBPase2 activity of the bifunctional enzyme and activates its PFK2 activity. [2] As a result, the production of fructose 2,6-bisphosphate increases, ultimately leading to an upregulation of glycolysis. [3]

Although previously thought of mainly as an intermediary in the pentose phosphate pathway, recent research reported that the sugar also has a role in gene expression, mainly by promoting the ChREBP transcription factor in the well-fed state. [4] [5] However, more recent study showed that D-glucose-6-phosphate, rather than D-xylulose-5-phosphate, is essential for the activation of ChREBP in response to glucose. [6]

Related Research Articles

<span class="mw-page-title-main">Glycolysis</span> Series of interconnected biochemical reactions

Glycolysis is the metabolic pathway that converts glucose into pyruvate and, in most organisms, occurs in the liquid part of cells. The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). Glycolysis is a sequence of ten reactions catalyzed by enzymes.

<span class="mw-page-title-main">Phosphorylation</span> Chemical process of introducing a phosphate

In biochemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology. Protein phosphorylation often activates many enzymes.

Gluconeogenesis (GNG) is a metabolic pathway that results in the biosynthesis of glucose from certain non-carbohydrate carbon substrates. It is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In vertebrates, gluconeogenesis occurs mainly in the liver and, to a lesser extent, in the cortex of the kidneys. It is one of two primary mechanisms – the other being degradation of glycogen (glycogenolysis) – used by humans and many other animals to maintain blood sugar levels, avoiding low levels (hypoglycemia). In ruminants, because dietary carbohydrates tend to be metabolized by rumen organisms, gluconeogenesis occurs regardless of fasting, low-carbohydrate diets, exercise, etc. In many other animals, the process occurs during periods of fasting, starvation, low-carbohydrate diets, or intense exercise.

Carbohydrate metabolism is the whole of the biochemical processes responsible for the metabolic formation, breakdown, and interconversion of carbohydrates in living organisms.

<span class="mw-page-title-main">Pyruvate kinase</span> Class of enzymes

Pyruvate kinase is the enzyme involved in the last step of glycolysis. It catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP), yielding one molecule of pyruvate and one molecule of ATP. Pyruvate kinase was inappropriately named before it was recognized that it did not directly catalyze phosphorylation of pyruvate, which does not occur under physiological conditions. Pyruvate kinase is present in four distinct, tissue-specific isozymes in animals, each consisting of particular kinetic properties necessary to accommodate the variations in metabolic requirements of diverse tissues.

<span class="mw-page-title-main">Glucose 6-phosphate</span> Chemical compound

Glucose 6-phosphate is a glucose sugar phosphorylated at the hydroxy group on carbon 6. This dianion is very common in cells as the majority of glucose entering a cell will become phosphorylated in this way.

In organic chemistry, a tetrose is a monosaccharide with 4 carbon atoms. They have either an aldehyde functional group in position 1 (aldotetroses) or a ketone group in position 2 (ketotetroses).

<span class="mw-page-title-main">Pentose phosphate pathway</span> Series of interconnected biochemical reactions

The pentose phosphate pathway is a metabolic pathway parallel to glycolysis. It generates NADPH and pentoses as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides. While the pentose phosphate pathway does involve oxidation of glucose, its primary role is anabolic rather than catabolic. The pathway is especially important in red blood cells (erythrocytes). The reactions of the pathway were elucidated in the early 1950s by Bernard Horecker and co-workers.

<span class="mw-page-title-main">Phosphofructokinase 2</span> Class of enzymes

Phosphofructokinase-2 (6-phosphofructo-2-kinase, PFK-2) or fructose bisphosphatase-2 (FBPase-2), is an enzyme indirectly responsible for regulating the rates of glycolysis and gluconeogenesis in cells. It catalyzes formation and degradation of a significant allosteric regulator, fructose-2,6-bisphosphate (Fru-2,6-P2) from substrate fructose-6-phosphate. Fru-2,6-P2 contributes to the rate-determining step of glycolysis as it activates enzyme phosphofructokinase 1 in the glycolysis pathway, and inhibits fructose-1,6-bisphosphatase 1 in gluconeogenesis. Since Fru-2,6-P2 differentially regulates glycolysis and gluconeogenesis, it can act as a key signal to switch between the opposing pathways. Because PFK-2 produces Fru-2,6-P2 in response to hormonal signaling, metabolism can be more sensitively and efficiently controlled to align with the organism's glycolytic needs. This enzyme participates in fructose and mannose metabolism. The enzyme is important in the regulation of hepatic carbohydrate metabolism and is found in greatest quantities in the liver, kidney and heart. In mammals, several genes often encode different isoforms, each of which differs in its tissue distribution and enzymatic activity. The family described here bears a resemblance to the ATP-driven phospho-fructokinases; however, they share little sequence similarity, although a few residues seem key to their interaction with fructose 6-phosphate.

<span class="mw-page-title-main">Transketolase</span> Enzyme involved in metabolic pathways

Transketolase is an enzyme that, in humans, is encoded by the TKT gene. It participates in both the pentose phosphate pathway in all organisms and the Calvin cycle of photosynthesis. Transketolase catalyzes two important reactions, which operate in opposite directions in these two pathways. In the first reaction of the non-oxidative pentose phosphate pathway, the cofactor thiamine diphosphate accepts a 2-carbon fragment from a 5-carbon ketose (D-xylulose-5-P), then transfers this fragment to a 5-carbon aldose (D-ribose-5-P) to form a 7-carbon ketose (sedoheptulose-7-P). The abstraction of two carbons from D-xylulose-5-P yields the 3-carbon aldose glyceraldehyde-3-P. In the Calvin cycle, transketolase catalyzes the reverse reaction, the conversion of sedoheptulose-7-P and glyceraldehyde-3-P to pentoses, the aldose D-ribose-5-P and the ketose D-xylulose-5-P.

The L-arabinose operon, also called the ara or araBAD operon, is an operon required for the breakdown of the five-carbon sugar L-arabinose in Escherichia coli. The L-arabinose operon contains three structural genes: araB, araA, araD, which encode for three metabolic enzymes that are required for the metabolism of L-arabinose. AraB (ribulokinase), AraA, and AraD produced by these genes catalyse conversion of L-arabinose to an intermediate of the pentose phosphate pathway, D-xylulose-5-phosphate.

<span class="mw-page-title-main">Ribose 5-phosphate</span> Chemical compound

Ribose 5-phosphate (R5P) is both a product and an intermediate of the pentose phosphate pathway. The last step of the oxidative reactions in the pentose phosphate pathway is the production of ribulose 5-phosphate. Depending on the body's state, ribulose 5-phosphate can reversibly isomerize to ribose 5-phosphate. Ribulose 5-phosphate can alternatively undergo a series of isomerizations as well as transaldolations and transketolations that result in the production of other pentose phosphates as well as fructose 6-phosphate and glyceraldehyde 3-phosphate.

<span class="mw-page-title-main">Fructose 2,6-bisphosphate</span> Chemical compound

Fructose 2,6-bisphosphate, abbreviated Fru-2,6-P2, is a metabolite that allosterically affects the activity of the enzymes phosphofructokinase 1 (PFK-1) and fructose 1,6-bisphosphatase (FBPase-1) to regulate glycolysis and gluconeogenesis. Fru-2,6-P2 itself is synthesized and broken down in either direction by the integrated bifunctional enzyme phosphofructokinase 2 (PFK-2/FBPase-2), which also contains a phosphatase domain and is also known as fructose-2,6-bisphosphatase. Whether the kinase and phosphatase domains of PFK-2/FBPase-2 are active or inactive depends on the phosphorylation state of the enzyme.

<span class="mw-page-title-main">Phosphopentose epimerase</span> Class of enzymes

Phosphopentose epimerase encoded in humans by the RPE gene is a metalloprotein that catalyzes the interconversion between D-ribulose 5-phosphate and D-xylulose 5-phosphate.

<span class="mw-page-title-main">6-phosphogluconolactonase</span> Cytosolic enzyme

6-Phosphogluconolactonase (EC 3.1.1.31, 6PGL, PGLS, systematic name 6-phospho-D-glucono-1,5-lactone lactonohydrolase) is a cytosolic enzyme found in all organisms that catalyzes the hydrolysis of 6-phosphogluconolactone to 6-phosphogluconic acid in the oxidative phase of the pentose phosphate pathway:

<span class="mw-page-title-main">Sucrose phosphorylase</span> Class of enzymes

Sucrose phosphorylase is an important enzyme in the metabolism of sucrose and regulation of other metabolic intermediates. Sucrose phosphorylase is in the class of hexosyltransferases. More specifically it has been placed in the retaining glycoside hydrolases family although it catalyzes a transglycosidation rather than hydrolysis. Sucrose phosphorylase catalyzes the conversion of sucrose to D-fructose and α-D-glucose-1-phosphate. It has been shown in multiple experiments that the enzyme catalyzes this conversion by a double displacement mechanism.

<span class="mw-page-title-main">Ribose-5-phosphate isomerase</span>

Ribose-5-phosphate isomerase (Rpi) encoded by the RPIA gene is an enzyme that catalyzes the conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P). It is a member of a larger class of isomerases which catalyze the interconversion of chemical isomers. It plays a vital role in biochemical metabolism in both the pentose phosphate pathway and the Calvin cycle. The systematic name of this enzyme class is D-ribose-5-phosphate aldose-ketose-isomerase.

<span class="mw-page-title-main">Carbohydrate-responsive element-binding protein</span> Protein found in humans

Carbohydrate-responsive element-binding protein (ChREBP) also known as MLX-interacting protein-like (MLXIPL) is a protein that in humans is encoded by the MLXIPL gene. The protein name derives from the protein's interaction with carbohydrate response element sequences of DNA.

<span class="mw-page-title-main">Inborn errors of carbohydrate metabolism</span> Medical condition

Inborn errors of carbohydrate metabolism are inborn error of metabolism that affect the catabolism and anabolism of carbohydrates.

<span class="mw-page-title-main">TP53-inducible glycolysis and apoptosis regulator</span> Protein-coding gene in the species Homo sapiens

The TP53-inducible glycolysis and apoptosis regulator (TIGAR) also known as fructose-2,6-bisphosphatase TIGAR is an enzyme that in humans is encoded by the C12orf5 gene.

References

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  2. Nelson, David L.; Cox, Michael M.; Nelson, David L. (2013). Lehninger, Albert L. (ed.). Lehninger principles of biochemistry (6th ed.). Basingstoke: Macmillan Higher Education. p. 606. ISBN   978-1-4292-3414-6.
  3. Uyeda K (June 2021). "Short- and Long-Term Adaptation to Altered Levels of Glucose: Fifty Years of Scientific Adventure". Annual Review of Biochemistry. 90 (1): 31–55. doi: 10.1146/annurev-biochem-070820-125228 . PMID   34153217.
  4. Kabashima T, Kawaguchi T, Wadzinski BE, Uyeda K (April 2003). "Xylulose 5-phosphate mediates glucose-induced lipogenesis by xylulose 5-phosphate-activated protein phosphatase in rat liver". Proceedings of the National Academy of Sciences of the United States of America. 100 (9): 5107–5112. Bibcode:2003PNAS..100.5107K. doi: 10.1073/pnas.0730817100 . PMC   154306 . PMID   12684532.
  5. Iizuka K, Horikawa Y (August 2008). "ChREBP: a glucose-activated transcription factor involved in the development of metabolic syndrome". Endocrine Journal. 55 (4): 617–624. doi: 10.1507/endocrj.k07e-110 . PMID   18490833.
  6. Dentin R, Tomas-Cobos L, Foufelle F, Leopold J, Girard J, Postic C, Ferré P (January 2012). "Glucose 6-phosphate, rather than xylulose 5-phosphate, is required for the activation of ChREBP in response to glucose in the liver". Journal of Hepatology. 56 (1): 199–209. doi:10.1016/j.jhep.2011.07.019. PMID   21835137.