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Amino acids are protein building blocks, abundant in nature and fundamental to life. In living organisms, amino acids are synthesised in sophisticated metabolic pathways that enable growth, repair and metabolism. But most amino acids, especially essential amino acids, need to be acquired through diet or supplementation. Amino acid synthesis also features prominently in contemporary science and industry. Thanks to the development of chemical synthesis and biosynthetic methods, natural amino acids and functionalized non-natural compounds can now be synthesized with a high purity. These synthesis technologies drive the food and pharmaceutical sectors, as well as new frontiers of biomaterials, cosmetics and agriculture.
Amino acids are organic compounds containing both an amino group (-NH₂) and a carboxyl group (-COOH). Their general structure can be represented as H₂N-CHR-COOH, where R represents the side chain. Different side chains endow amino acids with distinct properties and functions. Based on the structure and nature of the side chain, amino acids can be categorized into nonpolar amino acids, polar uncharged amino acids, acidic amino acids, and basic amino acids. For example, the side chain of alanine (Ala) is a simple methyl group (-CH₃), making it a nonpolar amino acid, whereas the side chain of glutamic acid (Glu) contains a carboxyl group (-CH₂CH₂COOH), classifying it as an acidic amino acid. These classifications help us understand the arrangement and interactions of amino acids within proteins, as well as their specific functions in various physiological processes. Generally, amino acid synthesis can be divided into two major categories: biological synthesis within living organisms and chemical synthesis through organic chemistry.
In living organisms, the synthesis of amino acids is a complex and precise process involving the coordinated action of multiple enzymes and metabolic pathways. Amino acid biosynthesis can be divided into two types: de novo synthesis and reutilization synthesis. De novo synthesis refers to the process by which organisms synthesize amino acids from simple precursors, such as carbohydrates and ammonia, through a series of enzyme-catalyzed reactions. Reutilization synthesis involves the breakdown of proteins or other nitrogen-containing compounds to release amino acids, which are then reused. The regulation of amino acid biosynthesis in organisms primarily occurs through feedback inhibition and enzyme induction. Feedback inhibition means that when the intracellular concentration of a particular amino acid increases, it inhibits the activity of key enzymes in its biosynthetic pathway, thereby reducing its production. Enzyme induction, on the other hand, occurs when cells require the synthesis of a specific amino acid, leading to the induction of the enzymes involved in its production. This regulatory mechanism allows organisms to precisely adjust amino acid synthesis according to their needs and environmental conditions, thereby avoiding unnecessary energy and material wastage.
From the perspective of organic chemistry, amino acids are organic compounds characterized by the presence of an amino group (-NH₂) and a carboxyl group (-COOH). These structural features determine their behavior in chemical reactions. The synthesis of amino acids involves various types of organic reactions, such as condensation reactions, reduction reactions, and oxidation reactions. These reactions form and break chemical bonds, linking different atoms or groups together to ultimately produce amino acid molecules. For example, in the synthesis of certain amino acids, condensation reactions between amino and carboxyl groups form peptide bonds, which are fundamental to protein synthesis. Additionally, the stability of chemical bonds influences both the reaction rate and the stability of the resulting amino acid products. For instance, the stability of double bonds in some amino acid precursors affects subsequent addition reactions, thereby impacting the efficiency of amino acid synthesis.
The industrial synthesis of amino acids primarily involves chemical synthesis, fermentation, and enzymatic catalysis. Chemical synthesis relies on chemical reactions to produce target amino acids and is suitable for large-scale production. Fermentation utilizes microorganisms, such as Escherichia coli or Corynebacterium glutamicum, to generate specific amino acids through metabolic processes, making it widely applicable in the food and pharmaceutical industries. Enzymatic catalysis, on the other hand, achieves efficient and environmentally friendly amino acid synthesis through the action of specific enzymes, particularly advantageous for the production of chiral amino acids.
Amino acid hydrolysis refers to the method of obtaining amino acids by hydrolyzing proteins or peptide chains. This process has wide applications in industries such as food and pharmaceuticals. Protein hydrolysis is typically carried out under acidic or alkaline conditions. Under acidic conditions, proteins are hydrolyzed into amino acids by strong acids like hydrochloric acid. This process requires high temperatures and extended times to ensure complete hydrolysis of the protein. For example, in the production of monosodium glutamate (MSG), soybean protein is hydrolyzed using hydrochloric acid, followed by steps such as neutralization and extraction to obtain glutamic acid, which is then converted into monosodium glutamate through fermentation or chemical synthesis. Under alkaline conditions, proteins can be hydrolyzed by strong bases like sodium hydroxide. The advantage of alkaline hydrolysis is its relatively fast reaction rate, but it may lead to the degradation of some amino acids, particularly those sensitive to alkali, such as serine (Ser) and threonine (Thr). Therefore, in practical applications, appropriate hydrolysis conditions should be chosen based on the properties and requirements of the target amino acids.
Chemical synthesis is a method for producing amino acids by combining organic synthesis and chemical engineering techniques. Its greatest advantage is that the types of amino acids produced are not limited, as it can be used to prepare both natural amino acids and a variety of non-natural amino acids with special structures. However, since chemical synthesis produces amino acids that contain both D- and L- optical isomers (chiral isomers), it is necessary to address the issue of isomer separation and the racemization of D-isomers during the synthesis process. Amino acids such as glycine, methionine, and tryptophan have already been industrialized for mass production using chemical synthesis methods. Common chemical synthesis methods include:
Amino acid fermentation is a method that utilizes the metabolic activities of microorganisms to produce amino acids. This method offers advantages such as high production efficiency, low cost, and environmental friendliness, and has become one of the main methods for large-scale amino acid production. In the amino acid fermentation process, the first step is to select appropriate microbial strains. Different amino acid fermentations require different strains. For example, Corynebacterium glutamicum is commonly used for glutamic acid fermentation, while Bacillus subtilis is often used for lysine fermentation. These strains possess efficient amino acid synthesis pathways and strong metabolic capabilities. The strains are then inoculated into a fermentation medium containing carbon sources, nitrogen sources, inorganic salts, and other nutrients, and fermentation is carried out under optimal conditions of temperature, pH, and aeration. During fermentation, microorganisms grow and carry out metabolic activities by absorbing nutrients from the medium, converting carbon sources into amino acids. After fermentation, amino acid products are obtained through processes such as separation and purification. Amino acid fermentation is not only used to produce common amino acids like glutamic acid, lysine, and threonine, but also for producing rare and functional amino acids, providing a rich source of raw materials for industries such as food, pharmaceuticals, and animal feed.
Enzymatic methods utilize the catalytic action of enzymes to convert substrates into the desired amino acids. Since the successful industrial production of L-aspartic acid using enzymatic methods in 1972, various amino acids have been produced using this approach. The advantages of enzymatic production include a simple production process, high product concentration, high conversion efficiency, minimal by-products, simplified extraction processes, high extraction yields, and the potential use of immobilized enzymes or immobilized cell technologies. Representative amino acids produced using enzymatic methods include alanine, aspartic acid, tyrosine, dopamine, tryptophan, 5-hydroxytryptophan, and lysine.
Amino acid synthesis typically varies depending on the type of reaction, as exemplified by the Strecker amino acid synthesis. This is a commonly used method for synthesizing α-amino acids, first proposed by German chemist Adolph Strecker in 1850. It involves the reaction of an aldehyde (or ketone) with ammonium chloride and potassium cyanide in an aqueous solution, generating α-amino nitrile, which is then hydrolyzed to yield the amino acid. The Strecker reaction includes the following key steps:
BOC Sciences offers comprehensive amino acid synthesis services, covering the custom production of both natural and non-natural amino acids to meet the needs of various industries. We have advanced synthesis platforms capable of precisely designing and synthesizing a wide range of amino acids and their derivatives, including labeled amino acids, protected amino acids, and chiral amino acids. Our services are widely used in pharmaceutical research and development, protein engineering, food additives, and materials science. With stringent quality control and flexible production capabilities, we can provide high-quality products from laboratory scale to industrial scale. Additionally, we offer process optimization, technical support, and fast delivery services to ensure the fulfillment of diverse project requirements.
Amino acid synthesis has broad applications in fields such as pharmaceuticals, food, and chemicals. In the pharmaceutical industry, it is used for producing amino acid-based drugs, nutritional supplements, and active molecules with anticancer, antibacterial, and other therapeutic properties. In the food industry, synthesized amino acids are used as flavor enhancers (e.g., monosodium glutamate) and nutritional fortifiers. In the chemical industry, amino acid synthesis is employed to prepare biodegradable materials and surfactants. Moreover, the synthesis of non-natural amino acids has driven advancements in protein engineering, antibody-drug conjugates, and novel biomarker development, supporting scientific research and industrial innovation.
In the pharmaceutical field, research on amino acid synthesis provides a crucial foundation for drug development. Many drugs exert their effects by regulating amino acid metabolism or protein synthesis. For example, certain anticancer drugs inhibit amino acid synthesis pathways in tumor cells, preventing tumor growth and proliferation. Additionally, amino acids themselves can act as drugs or drug precursors. For instance, arginine is used to treat hypertension and cardiovascular diseases, as it promotes nitric oxide synthesis, which dilates blood vessels.
In the food industry, research on amino acid synthesis contributes to the development of new food additives and nutritional supplements. Amino acids are essential nutrients for the human body, and by adding appropriate amounts of amino acids to food, the nutritional value of the food can be enhanced to meet the body's amino acid needs. Furthermore, amino acids can also be used for flavor enhancement and food preservation.
Additionally, research on amino acid synthesis can provide theoretical insights for protein engineering. By understanding the mechanisms and reactions of amino acid synthesis, protein structures and functions can be designed and modified, leading to the development of novel proteins with specific properties. For example, modifying the amino acid sequence of enzymes can improve their catalytic efficiency, stability, and specificity, leading to the development of more efficient biocatalysts.
Gene editing technologies, such as the CRISPR-Cas9 system, provide powerful tools for researching amino acid synthesis. Gene editing allows for the precise knockout or knock-in of genes related to amino acid synthesis, facilitating the study of gene functions and mechanisms. Additionally, gene editing can be used to modify microorganisms or cells to enhance the efficiency and yield of amino acid synthesis. For example, by editing the genome of microorganisms, the amino acid synthesis pathway can be optimized, reducing metabolic byproduct formation and increasing the yield of target amino acids.
Metabolomics technology enables comprehensive analysis of metabolic changes in organisms, offering new perspectives for amino acid synthesis research. Using metabolomics, dynamic changes in metabolites during amino acid synthesis can be monitored in real time, providing insights into the operation and regulation of metabolic pathways. Moreover, metabolomics can help identify new metabolic pathways and regulatory nodes, offering new ideas and targets for amino acid synthesis research.
Single-cell analysis technology allows for precise analysis of amino acid synthesis within individual cells, revealing cellular heterogeneity and individual differences. Through single-cell analysis, differences in amino acid synthesis can be studied in various cell types or physiological states, providing an understanding of the regulatory mechanisms and physiological functions of amino acid synthesis within cells. For example, in cancer research, single-cell analysis can uncover differences in amino acid synthesis between tumor cells and normal cells, providing new insights for cancer diagnosis and treatment.
