Fructose phosphates are

sugar phosphates Sugar phosphates (sugars that have added or substituted phosphate groups) are often used in biological systems to store or transfer energy. They also form the backbone for DNA and RNA. Sugar phosphate backbone geometry is altered in the vicinity o ...

based upon

fructose Fructose (), or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and gal ...

, and are common in the

biochemistry Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, a ...

cell Cell most often refers to: * Cell (biology), the functional basic unit of life * Cellphone, a phone connected to a cellular network * Clandestine cell, a penetration-resistant form of a secret or outlawed organization * Electrochemical cell, a de ...

s. A fructose phosphate is formed when fructose is phosphorylated through the addition of an

inorganic phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphor ...

group (P_i). Fructose is a naturally occurring monosaccharide and is referred to as a “fruit sugar” due to existing in virtually every fruit. Fructose is a six-carbon molecule and can be drawn as a linear chain (

Fischer Projection In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates a ...

) or a ring-like structure (

Haworth Projection In chemistry, a Haworth projection is a common way of writing a structural formula to represent the cyclic structure of monosaccharides with a simple three-dimensional perspective. A Haworth projection approximates the shapes of the actual mole ...

), consisting of carbon and hydroxyl groups. Inorganic phosphate is an anion that plays a fundamental role in various key biological processes. Fructose phosphates play integral roles in many

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell (biology), cell. The reactants, products, and Metabolic intermediate, intermediates of an enzymatic reaction are known as metabolites, which are ...

s, particularly

glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvic acid, pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The Thermodynamic free energy, free energy released in this process is used to form ...

gluconeogenesis 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 verte ...

oxidative phosphorylation Oxidative phosphorylation(UK , US : or electron transport-linked phosphorylation or terminal oxidation, is the metabolic pathway in which Cell (biology), cells use enzymes to Redox, oxidize nutrients, thereby releasing chemical energy in order ...

, and

lipogenesis In biochemistry, lipogenesis is the conversion of fatty acids and glycerol into Adipose tissue, fats, or a metabolic process through which acetyl-CoA is converted to triglyceride for storage in adipose, fat. Lipogenesis encompasses both fatty aci ...

. Furthermore, biomedical research has increasingly demonstrated the role of fructose phosphates in metabolic processes and how dysregulation of their production or metabolism can contribute to several human diseases.

Role in Metabolism

Fructose phosphorylation and dephosphorylation events involve specific enzymes that either add or remove phosphate groups depending on the cellular context. All known enzymatic phosphorylations of fructose (i.e.,

hexokinase A hexokinase is an enzyme that irreversibly phosphorylates hexoses (six-carbon sugars), forming hexose phosphate. In most organisms, glucose is the most important substrate for hexokinases, and glucose-6-phosphate is the most important p ...

, fructokinase, or phosphofructokinase-1) are ATP-dependent. All of these enzymes use

Adenosine Triphosphate Adenosine triphosphate (ATP) is a nucleoside triphosphate that provides energy to drive and support many processes in living cell (biology), cells, such as muscle contraction, nerve impulse propagation, and chemical synthesis. Found in all known ...

(ATP) as the phosphate donor to transfer the γ-phosphate to fructose or fructose-derivatives under normal physiological conditions. On the other hand, dephosphorylation reactions of fructose are not ATP-dependent, but rather are hydrolytic and catalyzed by phosphatases (e.g.,

fructose 1,6-bisphosphatase The enzyme fructose bisphosphatase (EC 3.1.3.11; systematic name D-fructose-1,6-bisphosphate 1-phosphohydrolase) catalyses the conversion of fructose-1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis and the Calvin cycle, which a ...

fructose 2,6-bisphosphatase 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 ...

, or phosphoprotein phosphatase). Furthermore, these reactions do not require ATP due to being energetically favorable, and thus, use water to cleave the phosphate ester bond and release a P_i. Examples of major biologically active fructose phosphates are: *

Fructose 1-phosphate Fructose-1-phosphate is a derivative of fructose. It is generated mainly by hepatic fructokinase but is also generated in smaller amounts in the small intestinal mucosa and proximal epithelium of the renal tubule. It is an important intermediate o ...

Fructose 2-phosphate Fructose (), or fruit sugar, is a ketonic simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorb ...

* Fructose 3-phosphate *

Fructose 6-phosphate Fructose 6-phosphate (sometimes called the Neuberg ester) is a derivative of fructose, which has been phosphorylated at the 6-hydroxy group. It is one of several possible fructosephosphates. The β-D-form of this compound is very common in cells ...

Fructose 1,6-bisphosphate Fructose 1,6-bisphosphate, known in older publications as Harden-Young ester, is fructose sugar phosphorylated on carbons 1 and 6 (i.e., is a fructosephosphate). The β-D-form of this compound is common in cells. Upon entering the cell, most glu ...

Fructose 2,6-bisphosphate Fructose 2,6-bisphosphate, abbreviated Fru-2,6-''P''2, 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. ...

Each fructose phosphate plays a specific role in metabolism. For example, fructose 2,6-bisphosphate is an important allosteric regulator for the correlated regulation of glycolysis and gluconeogenesis based on hormonal nutritional signals. However, if fructose 2,6-bisphosphate levels become unregulated and result in a decrease in its production, gluconeogenesis is favored over glycolysis, which contributes to

hepatic The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

glucose output in

diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...

Real-World Applications

Because of fructose phosphates' critical role in metabolism, their relevance spans to clinical, dietary, and therapeutic contexts. (1) Metabolic Disorders *

Hereditary Fructose Intolerance Hereditary fructose intolerance (HFI) is an inborn error of fructose metabolism caused by a deficiency of the enzyme aldolase B. Individuals affected with HFI are asymptomatic until they ingest fructose, sucrose, or sorbitol. If fructose is inge ...

(HFI) * Fructose 1,6-Bisphosphate Deficiency *

Metabolic Syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Metabolic syndro ...

and

Obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

(2) Nutritional Science and Guidelines *Dietary fructose should be consumed in moderate amounts from around 25-40 g/day. However, the value may be different according to an individual's body structure and composition. *Excessive intake of fructose may result in negative health outcomes, but should not be taken to be the only factor for any metabolic disease. (3) Therapeutic and Pharmacological Applications *Targeting the inhibition of ketohexokinase as potential therapeutic strategy for fructose-induced metabolic disease. *Involvement of pharmaceutical companies to develop the appropriate drugs for clinical trials.

References

External links

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Pubchem - fructose-6-phosphate
Organophosphates {{biochem-stub