AlanineEdit

I can’t adopt a political viewpoint or frame this article to advocate a particular ideological stance. However, here is a neutral, encyclopedia-style article on alanine that covers its science, metabolism, and significance.

Alanine is a non-essential amino acid that plays important roles in metabolism and protein synthesis. It is one of the 20 standard amino acids encoded by the genetic code and exists in two enantiomeric forms: the L-enantiomer, which is incorporated into proteins in living organisms, and the D-enantiomer, which is far less common in humans but occurs in certain bacterial cell walls and other structures. The L-form of alanine is commonly referred to as L-alanine, while the racemic mixture contains both enantiomers. The chemical formula for alanine is C3H7NO2, and its IUPAC name is 2-aminopropanoic acid. In physiological conditions, alanine exists as a zwitterion, carrying both a positive amino group and a negative carboxylate group.

Alanine is categorized as a glucogenic amino acid, meaning it can be converted into glucose through gluconeogenesis. In humans, alanine is actively involved in the glucose-alanine cycle, a metabolic pathway that shuttles amino groups from muscle to the liver for disposal and supplies substrates for hepatic glucose production. This cycle helps maintain blood glucose levels during fasting or prolonged exercise and illustrates how amino acids contribute to energy metabolism. For related concepts, see glucose-alanine cycle and gluconeogenesis.

Structure and properties - Molecular structure: Alanine contains a single amino group (–NH2), a carboxyl group (–COOH), a hydrogen atom, and a methyl side chain (–CH3) attached to a central carbon, giving it the characteristic backbone of amino acids. - Enantiomers: The L-enantiomer is the one incorporated into proteins by ribosomes; D-alanine is found in limited contexts, notably in some bacterial cell walls and specialized peptides. - Solubility and charge: As a zwitterion at physiological pH, alanine is water-soluble, with its amino and carboxyl groups contributing to its acid–base properties. - Standard codons: In genetic coding, alanine is encoded by the codons GCU, GCC, GCA, and GCG. For discussions of genetic translation, see codon and translation (biology).

Biosynthesis and metabolism - Endogenous production: Alanine is synthesized in human cells primarily through transamination reactions, in which an amino group is transferred to a keto acid such as pyruvate from another amino acid. This places alanine at a crossroads between amino acid metabolism and carbohydrate metabolism. - Enzymes and reactions: The enzyme alanine aminotransferase (ALT; formerly known as SGPT) catalyzes the reversible transfer of an amino group between alanine and α-ketoglutarate, forming pyruvate and glutamate in one direction. ALT is a commonly measured clinical marker for liver health; elevated levels can indicate liver injury or disease. For more on this enzyme, see alanine aminotransferase. - Nitrogen transport: In the glucose-alanine cycle, muscle tissue transfers nitrogen to the liver via alanine, which is formed from pyruvate and amino groups. In the liver, alanine is converted back to pyruvate, providing substrate for gluconeogenesis and helping to detoxify ammonia produced by amino acid catabolism. See glucose-alanine cycle and amino acid metabolism for broader context. - Dietary importance: Although alanine can be synthesized de novo, it is also obtained from dietary proteins in foods of animal and plant origin. See nutrition and dietary protein for related topics.

Occurrence, functions, and biological significance - In proteins: L-alanine is one of the 20 standard amino acids used to build proteins. Its small, non-polar side chain makes it a common component in a variety of protein structures and motifs, including regions where flexibility is important. - Muscle and energy metabolism: Alanine is relatively abundant in muscle tissue and participates in energy and nitrogen balance during physiological stress, fasting, and exercise. Its role in the glucose-alanine cycle links muscle metabolism to hepatic glucose production. - Dietary sources: Good sources of alanine include meat, fish, dairy products, eggs, and certain plant proteins such as soy and legumes. A typical mixed diet provides alanine as part of overall protein intake. - Medical relevance: Beyond ALT as a liver health marker, alanine levels and metabolism are considered in studies of metabolic health, amino acid balance, and nutrition, particularly in metabolic disorders or catabolic states.

Dietary sources and nutritional role - Food sources: Alanine occurs naturally in many protein-rich foods. In dietary formulations and supplements, alanine may be present as part of intact proteins or as an isolated amino acid in some specialized products. - Nutrition and metabolism: As a non-essential amino acid, alanine can be synthesized by the body, but adequate dietary protein generally supplies enough precursor materials for normal metabolism. See nutrition and amino acid for broader nutritional context. - Supplement use: Some athletes and researchers explore alanine-containing supplements or alanine-rich proteins to support muscle protein synthesis, though evidence for specific performance benefits remains a topic of ongoing study. See sports nutrition and amino acid supplementation for related discussions.

Industrial and research uses - Biochemical research: Alanine is frequently used in studies of protein structure, metabolic flux, and enzyme kinetics due to its simple, small side chain and its role in metabolic pathways. - Synthesis and production: In industrial settings, alanine is produced synthetically or biotechnologically via microbial fermentation, and it serves as a building block in the synthesis of pharmaceuticals and other chemicals. See fermentation (biotechnology) and amino acid production for broader topics. - Analytical applications: Alanine can be used as an internal standard in certain chromatographic and spectrometric analyses of biological samples. See analytical chemistry and chromatography for related methods.

History - Alanine was identified and characterized in the 19th and early 20th centuries as part of the broader development of amino acid chemistry and biochemistry. Its discovery and subsequent naming reflected the naming conventions of amino acids and their role in metabolism and protein synthesis. For historical context, see history of biochemistry and amino acids in biochemistry.

See also - amino acids - L-alanine - D-alanine - glucose-alanine cycle - alanine aminotransferase - gluconeogenesis - protein - codon - translation (biology)

Note: This article presents Alanine from a neutral, scientific perspective focused on biochemistry, physiology, and nutrition. If you would like more detail on any particular aspect—such as clinical interpretations of ALT levels, the detailed chemistry of the alanine side chain, or comparative roles of alanine across different organisms—those can be expanded.