Lysine (Essential amino acid)
Lysine is an α-amino acid that is used in the biosynthesis of proteins. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet.
Lysine is a base, as are arginine and histidine. The ε-amino group often participates in hydrogen bonding and as a general base in catalysis. The ε-ammonium group (NH3+) is attached to the fourth carbon from the α-carbon, which is attached to the carboxyl (C=OOH) group.
Lysine is particularly useful in therapy for marasmus (wasting).
Lysine is particularly useful in therapy for marasmus (wasting) and herpes simplex. It stops the growth of herpes simplex in culture, and has helped to reduce the number and occurrence of cold sores in clinical studies.
The mechanism underlying the effect of lysine on herpes simplex virus is based on the viral need for amino acid arginine; lysine competes with arginine for absorption and entry into cells. Lysine inhibits HSV growth by knocking out arginine. Therefore, diets high in lysine and low in arginine can be useful in the prevention and treatment of herpes.
However, an authoritative Cochrane Review published in 2015 concluded there is insufficient evidence that lysine supplementation is effective against herpes simplex virus; it has not been approved by the FDA for herpes simplex suppression.
Lysine also may be a useful adjunct in the treatment of osteoporosis because it reduces calcium losses in urine. L-Lysine plays a major role in calcium absorption; building muscle protein; recovering from surgery or sports injuries; and the body's production of hormones, enzymes, and antibodies.
Allysine is a derivative of lysine, used in the production of elastin and collagen. It is produced by the actions of the enzyme lysyl oxidase on lysine in the extracellular matrix and is essential in the crosslink formation that stabilizes collagen and elastin.
Of meat products, wild game and pork have the highest concentration of lysine
Lysine is supplied by many foods, especially red meats, fish, and dairy products. Lysine is also high in foods such as wheat germ, and chicken. Of meat products, wild game and pork have the highest concentration of lysine. Fruits and vegetables contain little lysine, except avocados.
Good sources of lysine are generally high-protein foods such as eggs, meat (specifically red meat, lamb, pork, and poultry), soy, beans and peas, cheese (particularly Parmesan), and certain fish (such as cod and sardines).
Lysine is the limiting amino acid (the essential amino acid found in the smallest quantity in the particular foodstuff) in most cereal grains, but is plentiful in most pulses (legumes). A vegetarian or low animal protein diet can be adequate for protein, including lysine, if it includes both cereal grains and legumes, but there is no need for the two food groups to be consumed in the same meals.
A food is considered to have sufficient lysine if it has at least 51 mg of lysine per gram of protein (so that the protein is 5.1% lysine). Foods containing significant proportions of lysine include:
(Fish 9.19%); (Beef, ground, 90% lean/10% fat, cooked 8.31%); (Chicken, roasting, meat and skin, cooked, roasted 8.11%); (Azuki bean (adzuki beans), mature seeds, raw 7.53%); (Milk, non-fat 7.48%); (Soybean, mature seeds, raw 7.42%); (Egg, whole, raw 7.27%); (Pea, split, mature seeds, raw 7.22%); (Lentil, pink, raw 6.97%); (Kidney bean, mature seeds, raw 6.87%); (Chickpea, (garbanzo beans, Bengal gram), mature seeds, raw 6.69%); (Navy bean, mature seeds, raw 5.73%).
Although high protein diets result in loss of large amounts of calcium in urine, so does lysine deficiency.
Normal lysine metabolism is dependent upon many nutrients including niacin, vitamin B6, riboflavin, vitamin C, glutamic acid and iron. Excess arginine antagonizes lysine. Several inborn errors of lysine metabolism are known, such as cystinuria, hyperdibasic aminoaciduria I, lysinuric protein intolerance, propionic acidemia, and tyrosinemia I. Most are marked by mental retardation with occasional diverse symptoms such as absence of secondary sex characteristics, undescended testes, abnormal facial structure, anemia, obesity, enlarged liver and spleen, and eye muscle imbalance.
Although high protein diets result in loss of large amounts of calcium in urine, so does lysine deficiency. Lysine may be an adjunct therapy because it reduces calcium losses in urine. Lysine deficiency also may result in immunodeficiency. Requirements for this amino acid are probably increased by stress.
Low lysine levels have been found in patients with Parkinson's, hypothyroidism, kidney disease, asthma and depression. The exact significance of these levels is unclear, yet lysine therapy can normalize the level and has been associated with improvement of some patients with these conditions.
Dosing of lysine has not been adequately studied, but beneficial clinical effects occur in doses ranging from 100 mg to 4 g a day.
Lysine toxicity has not occurred with oral doses in humans. Lysine dosages are presently too small and may fail to reach the concentrations necessary to prove potential therapeutic applications. Lysine metabolites, amino caproic acid and carnitine have already shown their therapeutic potential. Thirty grams daily of amino caproic acid has been used as an initial daily dose in treating blood clotting disorders, indicating that the proper doses of lysine, its precursor, have yet to be used in medicine.
Dosing of lysine has not been adequately studied, but beneficial clinical effects occur in doses ranging from 100 mg to 4 g a day. Higher doses may also be useful, and toxicity has not been reported in doses as high as 8 g per day.
Normal requirements for lysine have been found to be about 8 g per day or 12 mg/kg in adults. Children and infants need more, 44 mg/kg per day for an eleven to-twelve-year old, and 97 mg/kg per day for three-to six-month old.