lysine(redirected from Amino acid K)
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lysine(lī`sēn), organic compound, one of the 20 amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
..... Click the link for more information. commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein. It is one of several essential amino acids needed in the diet; the human body cannot synthesize it from simpler metabolites. Young adults need about 23 mg of this amino acid per day per kilogram (10 mg per lb) of body weight. Lysine is found in particularly low concentrations in the proteins of cereals; wheat gluten, for example, is relatively poor in lysine. This deficiency in lysine is the reason for the failure of diets in some parts of the world that employ cereal protein as a sole source of essential amino acids to support growth in children and general well-being in adults. Attempts to develop lysine-rich corn have been partly successful. Once lysine is incorporated into protein, its basic side chain often provides a positive electrical charge to the protein, thereby aiding its solubility in water. Its side chain has also been implicated in the binding of several coenzymescoenzyme
, any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes. A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in
..... Click the link for more information. (pyridoxal phosphate, lipoic acid, and biotin) to enzymesenzyme,
biological catalyst. The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the attention of many 19th-century chemists.
..... Click the link for more information. . It also plays an important role in the functioning of histoneshistone
, any of a class of protein molecules found in the chromosomes of eukaryotic cells. They complex with the DNA (see nucleic acid) and pack the DNA into tight masses of chromatin, which have the structure of coiled coils, much like a tangled telephone cord.
..... Click the link for more information. . The amino acid was first isolated from casein (milk protein) in 1889, and its structure was elucidated in 1902.
(a, ε-diaminocaproic acid), a diaminomonocarboxylic amino acid; colorless crystals. Molecular weight, 146.19:
Lysine exists in two optically active D and L forms. Natural L-lysine (melting point, 224°-225°C, with decomposition) is readily soluble in water, acids, and bases, but only slightly soluble in alcohol. Lysine was extracted from casein hydrolysate in 1889 and synthesized in 1902. It is a component of nearly all proteins of animal and vegetable origin (large quantities in histones and protamines and small amounts in cereal proteins).
Lysine is an essential amino acid and not synthesized in the human or animal body. A lysine deficiency in the diet retards growth in children; in adults, it leads to a negative nitrogen balance and disturbances in the normal vital activities of the organism. In adults, the daily lysine requirement is 23 mg per kg body weight, in children, 170 mg per kg.
Microbiological synthesis is used for the industrial preparation of lysine, which is used to enrich fodder (for farm animals) and certain food products.