|
||||||||||||||||||||||
|
||||||||||||||||||||||
Pyruvate kinase is an enzyme involved in glycolysis. The Protein Data Bank ( PDB) is a repository for 3-D structural data of Proteins and Nucleic acids These data typically obtained by X-ray crystallography Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described The Human Genome Organisation (HUGO is an organization involved in the Human Genome Project, a project about mapping the human genome Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a Chromosome 1 is the designation for the largest Human Chromosome. The Entrez Global Query Cross-Database Search System is a powerful Federated search engine or Web portal that allows users to search many discrete Health sciences The National Center for Biotechnology Information ( NCBI) is part of the United States National Library of Medicine (NLM a branch of the National Institutes Swiss-Prot is a manually curated Biological database of Protein sequences The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them This article is about the Enzyme Commission codes For the European Commission system for coding chemicals see EC-No. The Human Genome Organisation (HUGO is an organization involved in the Human Genome Project, a project about mapping the human genome Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a Chromosome 15 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome The Entrez Global Query Cross-Database Search System is a powerful Federated search engine or Web portal that allows users to search many discrete Health sciences The National Center for Biotechnology Information ( NCBI) is part of the United States National Library of Medicine (NLM a branch of the National Institutes Swiss-Prot is a manually curated Biological database of Protein sequences The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them This article is about the Enzyme Commission codes For the European Commission system for coding chemicals see EC-No. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins See also Gluconeogenesis, which carries out a process wherein glucose is synthesized rather than catabolized It catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to ADP, yielding one molecule of pyruvate and one molecule of ATP. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst A phosphate, an Inorganic chemical, is a salt of Phosphoric acid. Phosphoenolpyruvate (synonyms phosphoenolpyruvic acid, PEP) is an important Chemical compound in Biochemistry. Adenosine diphosphate, abbreviated ADP, is a Nucleotide. It is an Ester of Pyrophosphoric acid with the Nucleoside Adenosine Pyruvic acid (CH3COCO2H is an alpha-keto acid. The Carboxylate Anion of pyruvic acid is known as pyruvate. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy
Contents |
Reaction
The reaction with pyruvate kinase:
pyruvate
kinase
PEP ----------> pyruvate
/ \
ADP ATP
This process also requires a manganese ion. The enzyme is a transferase under the international classification of enzymes.
This step is the final one in the glycolytic pathway, which produces pyruvate molecules. The pyruvate may next be used to regenerate NAD+ via fermentation, or can be converted (as acetyl CoA) to ATP. Acetyl-CoA is an important molecule in metabolism used in many biochemical reactions
Regulation
This reaction has a large negative free energy change, one of three in glycolysis. Free energy may refer to In science: Thermodynamic free energy, the energy in a physical system that can be converted to do work in particular All three such steps regulate the overall activity of the pathway, and are generally irreversible under physiological conditions.
Pyruvate kinase activity is regulated by:
- Its own substrate PEP and fructose 1,6-bisphosphate, an intermediate in glycolysis; which both enhance enzymatic activity. Fructose 16-phosphate is Fructose sugar Phosphorylated on carbons 1 and 6 (ie Thus, glycolysis is driven to operate faster when more substrate is present.
- Citrate and ATP, which allosterically inhibit it. A citrate can refer either to the Conjugate base of Citric acid, (C3H5O(COO33&minus or to the Esters of citric This accounts for parallel regulation with PFK 1. Phosphofructokinase-1 (PFK-1 is the most important regulatory Enzyme ( of Glycolysis.
- Alanine, a negative allosteric modulator
Pyruvate kinase is also regulated indirectly by insulin and glucagon, which control a protein kinase. Alanine (abbreviated as Ala or A) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH3 Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance Glucagon is an important Hormone involved in Carbohydrate metabolism. A protein kinase is a Kinase Enzyme that modifies other Proteins by chemically adding Phosphate groups to them ( Phosphorylation) This protein kinase phosphorylates pyruvate kinase to inactivate it and dephosphorylates the enzyme to activate it. Glucagon signals fasting (no glucose available), and insulin signals the opposite. These two signaling molecules--in conjunction with the protein kinase--prevent pyruvate kinase from being active at the same time as the enzymes which catalyze the reverse reaction (pyruvate carboxylase and phosphoenolpyruvate carboxykinase), preventing a futile cycle. Pyruvate carboxylase is an Enzyme of the Ligase class that Catalyzes the irreversible Carboxylation of Pyruvate to form Oxaloacetate Not to be confused with Phosphoenolpyruvate carboxylase, PEPC Phosphoenolpyruvate carboxykinase (or PEPCK) is an Enzyme A Futile cycle is when two Metabolic pathways run simultaneously in opposite directions and have no overall effect other than wasting energy
In fact, to say that the forward reaction and reverse reaction are not both active simultaneously may not be entirely accurate. Futile cycles, also known as substrate cycles, are known to fine-tune flux through metabolic pathways.
Deficiency
Genetic defects of this enzyme cause the disease known as pyruvate kinase deficiency. Pyruvate kinase deficiency, also called erythrocyte piruvate kinase deficiency, is an Inherited Metabolic disorder of the enzyme Pyruvate kinase In this condition, a lack of pyruvate kinase slows down the process of glycolysis. This effect is especially devastating in cells that lack mitochondria, because these cells must use anaerobic glycolysis as their sole source of energy because the TCA cycle is not available. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Fermentation is the process of deriving energy from the oxidation of organic compounds such as carbohydrates using an endogenous electron acceptor which is The citric acid cycle, also known as the tricarboxylic acid cycle ( TCA cycle) or the Krebs cycle, (or rarely the Szent-Györgyi–Krebs cycle
One example is red blood cells, which in a state of pyruvate kinase deficiency rapidly become deficient in ATP and can undergo hemolysis. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood Hemolysis (or haemolysis)—from the Greek Hemo-, Greek meaning blood - Lysis, meaning to break open—is the breaking Therefore, pyruvate kinase deficiency can cause hemolytic anemia. Hemolytic anemia is Anemia due to Hemolysis, the abnormal breakdown of Red blood cells (RBCs either in the Blood vessels (intravascular hemolysis
Role in gluconeogenesis
Pyruvate kinase also serves as a regulatory enzyme for gluconeogenesis, a biochemical pathway in which the liver generates glucose from pyruvate and other substrates. Gluconeogenesis (abreviated GNG) is a Metabolic pathway that results in the generation of Glucose from non- Carbohydrate carbon substrates such Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. When pyruvate kinase is inhibited by phosphorylation (which occurs in the fasting state, via glucagon), phosphoenolpyruvate is prevented from conversion to pyruvate. Phosphorylation is the addition of a Phosphate (PO4 group to a Protein molecule or a small molecule Fasting is primarily the act of willingly abstaining from some or all Food, Drink, or both for a period of time Glucagon is an important Hormone involved in Carbohydrate metabolism. Instead, it is converted to glucose in a series of gluconeogenesis reactions that are mostly (but not exactly) the reverse sequence of glycolysis.
The glucose thus produced is expelled from the liver, providing energy for vital tissues in the fasting state.
See also
External links
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic