The function and application of valine
【Background and overview】
GorupBesanty first discovered valine in the extract of pancreas in 1856, and Fischer successfully separated valine from protein hydrolyzate in 1901. Valine is a branched non-polar α-amino acid containing five carbon atoms, its chemical name is α-amino-3-methylbutyric acid, the molecular formula is C 5 H 11 NO 2 , and the molecular weight is 117.15. Valine is white monoclinic crystal or crystalline powder, odorless with special bitter taste, melting point 315℃, stable to heat, light and air, easily soluble in water, almost insoluble in absolute ethanol and ether, and leucine. Acid separation is difficult. Valine is an optically active compound and is divided into L-type and D-type. Chemically synthesized methionine is L-form. L-valine is one of the 20 amino acids that make up protein, and is an essential amino acid and glycogenic amino acid for mammals. D-valine is present in some actinomycins such as valomycin. In animals, L-type is easily absorbed by the intestinal wall, and its physiological effect is twice that of D-type. Valine is also one of the three branched-chain amino acids, and has a wide range of applications in human nutritional additives, feed additives, condiments, medicines, pesticides and health care products.
The rational addition and utilization of valine in livestock and poultry production still needs further research and discussion in the following aspects: ① Improvement and synergy of valine production process. At present, valine has reached industrial production, but due to the limitation of production technology, the market price of valine is high, which increases the cost of feed cost; ② Further in-depth study of the nutritional metabolism and physiological effects of valine 3) Prove the relationship between valine and other nutrients in the diet and hormones in animals; 4) At each growth stage of livestock and poultry, the valine required in the diet is the most The appropriate amount of addition and its effect, and the concentration or level of other nutrients at the determined valine level.
【Absorption and Metabolism】
Valine enters the animal body and is rapidly and actively absorbed in the small intestine through the Na+-amino acid-carrier complex, and the absorption sites are mainly the duodenum and ileum. Metabolic transformation does not occur in the small intestinal mucosa, while in skeletal muscle metabolism, skeletal muscle is the main site for the transamination of branched-chain amino acids. After the valine in the diet is fed, digested and absorbed by animals, three branched-chain amino acids are used as substrates under the action of branched-chain amino acid transaminase to generate the corresponding branched-chain keto acid (BCKA) and glutamic acid (Glu). ), the amino group of Glu is finally used to synthesize the carrier of amino group - glutamine. BCKA is mainly transported to the liver for metabolism, undergoes oxidative decarboxylation and a series of degradation processes, and finally is converted into succinyl CoA through methylmalonyl CoA and enters the tricarboxylic acid cycle, which can be converted into oxaloacetate, so valine is Glycogenic amino acids, which mainly synthesize protein in the body and provide the energy required by the body, the product glutamine and the intermediate product alanine can undergo gluconeogenesis through the alanine-glucose cycle to maintain blood sugar concentration.
【Biological function and application】
1. Effects on protein metabolism: BCAAs can promote protein synthesis and inhibit its decomposition. Some researchers believe that branched-chain amino acids promote protein synthesis by promoting the initiation of polypeptide chain synthesis. Branched-chain amino acids have no effect on skeletal muscle protein degradation, but have inhibitory effects on protein degradation outside skeletal muscle.
2. Influence on the body's energy metabolism: In addition to being used for protein synthesis in the body, valine is also an important source of energy in the body during special physiological periods such as hunger, lactation, exercise, disease, especially during stress, branched-chain amino acids. It promotes the increased utilization of two important gluconeogenic amino acids, accelerates the energy conversion of hepatic gluconeogenesis, and reduces the concentration of alanine and glutamic acid in serum. Long-lasting energy source, long-lasting exercise ability, and prolonged fatigue time.
3. Effects on animal performance
1) Effects on poultry production performance: As one of the essential amino acids in animals, it is an amino acid necessary for poultry growth and feather development. Studies have shown that in broiler diets based on wheat or barley,
And in corn-based broiler diets, valine is also a limiting amino acid.
2) Effects on pig production performance: Studies have shown that valine is very important for lactating sows. Increasing the level of valine in the feed can increase milk production and litter weight gain, especially for sows with more than 10 weaned piglets. Valine requirements are much higher than those recommended by feeding standards and are related to lysine levels. When the level of lysine in the feed exceeds 0.8%, valine becomes the first limiting amino acid in the feed for lactating sows.
3) Effects on the production performance of ruminants: valine is an important nutrient in dairy cows and is closely related to production performance. Studies have confirmed that the biological function of valine in cattle is similar to that of pigs, and it plays the role of oxidative energy supply, regulating amino acid and protein metabolism, improving lactation performance and enhancing immunity. Studies have confirmed that valine can provide energy for bovine mammary gland tissue and provide carbon and alpha-amino nitrogen for the synthesis of non-essential amino acids. In addition, studies have reported that when the metabolizable protein of beef cattle in the growing period contains 5.7% valine, 5.6% isoleucine and 6.9% leucine, it can meet the nutritional needs of beef cattle and achieve the best economic benefits. as branched-chain amino acids.
4. Effects on endocrine function: The content of valine in the diet can also affect the endocrine level of animals. Studies have shown that supplementation of valine in the diets of lactating sows and lactating rats increases plasma prolactin and growth hormone concentrations. The study also confirmed that dietary supplementation of valine significantly increased sow serum prolactin concentrations, and increased skim milk insulin and skim milk growth hormone concentrations.
5. Regulating effect on nerve function: valine also plays an important role in the regulation of nerve function in animals. Studies in mice have also found that valine may be closely related to neural activity. When valine is insufficient , the function of the central nervous system of rats will be disordered, ataxia will cause tremors in the limbs, and uremia may be caused by the lack of ketoacid decarboxylase in the body's metabolic process, and the corresponding ketoacids will be excluded in the urine. Symptoms, such as convulsions, etc. Studies have shown that intravenous injection of branched-chain amino acids mixed in a ratio of 1:1:1 can increase the tolerance of mice to thermal stimulation, indicating that the branched-chain amino acid mixture has anti-pain properties.
6. Anti-tumor effect: Like normal tissue cells, tumor tissue cells need a large amount of specific nutrients to meet the needs of rapid growth. Branched-chain amino acids play an important role in the growth and differentiation of tumor cells. Among them, the high intake of valine It is one of the characteristics of tumor amino acid metabolism. The growth of tumor cells requires a large amount of valine. The relative deficiency caused by the limitation of valine can lead to the retardation of tumor cell structural protein and enzyme protein synthesis, block energy metabolism, lack of adenosine triphosphate, and increase cell membrane permeability, making it easier for anticancer drugs to enter cells. , further interfere with cell metabolism, block nucleic acid metabolism, and block DNA synthesis.