What is Lysine

Chemical Name:(S)-2,6-diaminohexanoic acid hydrochloride

Molecular Weight:182.65

Structrual Formula:

Nitrogen Content: 15.34%

Lysine is an essential amino acid found in both plant and animal foods. Lysine is necessary for proper growth, so it’s especially important to get enough of this amino acid during infancy and adolescence.

Lysine is basically alanine with a propylamine substituent on the ß-carbon. The e-amino group has a significantly higher pK a (about 10.5 in polypeptides) than does the a-amino group.

The amino group is highly reactive and often participates in a reactions at the active centers of enzymes (13). Proteins only have one a amino group, but numerous e amino groups. However, the higher pK a renders the lysyl side chains effectively less nucleophilic. Specific environmental effects in enzyme active centers can lower the pKa of the lysyl side chain such that it becomes reactive.

Note that the side chain has three methylene groups, so that even though the terminal amino group will be charged under physiological conditions, the side chain does have significant hydrophobic character. Lysines are often found buried with only them e-amino group exposed to solvent.

Lysine in Food

Good sources of lysine include red meat, poultry sardines, cheese, nuts, eggs, and legumes. Cereal grains tend to be low in lysine, which is why in these foods lysine is called the “limiting amino acid”—it is the amino acid that is present in the least amount relative to what’s needed for the body to make new protein.

Lysine Supplement

Signs of a lysine deficiency (14) include fatigue, nausea, dizziness, appetite loss, anxiety, decreased immunity and slow growth. People who have inadequate protein intake, and strict vegetarians whose diets lack legumes and do not include a wide variety of foods, may need more lysine-and amino acids in general. In that case, a supplement that provides a combination of amino acids would be a better choice that single amino acid supplements (245). The chance of creating an amino acid imbalance in the body are greater when taking single amino acids, and imbalances can interfere with the absorption of dietary amino acids.

The estimated adult requirement for lysine is 12 mg per kg of body weight (247). Again, as with some of the other amino acids, some experts feel that the requirement is set too low. The National Academy of Sciences acknowledges that the state of knowledge concerning amino acid requirements is “unsatisfactory” and expresses the hope that continuing research in the field will yield additional information for consideration. There is no information on the specific amino acid requirements for pregnant or lactating women, and the requirements for older people are considered to be the same as for younger adults.

Lysine – amino acid against herpes (190, 191, 192, 193)

L-lysine is an amino acids with a pharmacological use much more specific than that of most other amino acids. So far, supplementation of l-lysine is one of the best options available for the treatment of herpes simplex virus infections (246), especially oral forms. L-lysine is also much cheaper than antiviral drugs such as Acyclovir. L-lysine supplementation works by tilting the balance between lysine and arginine heavily in favor of lysine. This ameliorates herpes outbreaks because the herpes virus depends on the presence of arginine for its replication (246).

Lysine in combination with arginine is used by bodybuilders for the combination’s alleged effect of stimulating the release of growth hormone (232).

Lysine has also been shown to be useful in the prevention of atherosclerosis (231), a hardening of the walls of arteries caused by deposits of lipoproteins (fats). Lysine may be capable of loosening and preventing such deposits, therefore keeping artery walls flexible. Thus, there is less susceptibility for hypertension (high blood pressure). Hypertension is a major factor in heart attack and stroke.

Lysine Catabolism (237)

Lysine catabolism is unusual in the way that the a -amino group is transferred to a -ketoglutarate and into the general nitrogen pool. The reaction is a transamination in which the a -amino group is transferred to the a -keto carbon of a -ketoglutarate forming the metabolite, saccharopine . Unlike the majority of transamination reactions, this one does not employ pyridoxal phosphate as a cofactor. Saccharopine is immediately hydrolyzed by the enzyme ?-aminoadipic semialdehyde synthase in such a way that the amino nitrogen remains with the a -carbon of a -ketoglutarate, producing glutamate and a -aminoadipic semialdehyde. Because this transamination reaction is not reversible, lysine is an essential amino acid. The ultimate end-product of lysine catabolism is acetoacetyl-CoA.

Genetic deficiencies in the enzyme a -aminoadipic semialdehyde synthase have been observed in individuals who excrete large quantities of urinary lysine and some saccharopine. The lysinemia and associated lysinuria are benign. Other serious disorders associated with lysine metabolism are due to failure of the transport system for lysine and the other dibasic amino acids across the intestinal wall. Lysine is essential for protein synthesis; a deficiencies of its transport into the body can cause seriously diminished levels of protein synthesis. Probably more significant however, is the fact that arginine is transported on the same dibasic amino acid carrier, and resulting arginine deficiencies limit the quantity of ornithine available for the urea cycle. The result is severe hyperammonemia after a meal rich in protein. The addition of citrulline to the diet prevents the hyperammonemia.

Lysine is also important as a precursor for the synthesis of carnitine , required for the transport of fatty acids into the mitochondria for oxidation. Free lysine does not serve as the precursor for this reaction, rather the modified lysine found in certain proteins. Some proteins modify lysine to trimethyllysine using SAM as the methyl donor to transfer methyl groups to the a -amino of the lysine side chain. Hydrolysis of proteins containing trimethyllysine provide the substrate for the subsequent conversion to carnitine.

Lysine and muscle protein recovery (139)

Lysine and Infertility (146, 147, 148, 149)


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