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n. (context amino acid English) An essential amino acid C6H14N2O2.


n. an essential amino acid found in proteins; occurs especially in gelatin and casein


Lysine (abbreviated as Lys or K), encoded by the codons AAA and AAG) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO form under biological conditions), and a side chain lysyl ((CH)NH), classifying it as a charged (at physiological pH), aliphatic amino acid. 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-amino group (NH) is attached to the fifth carbon from the α-carbon, which is attached to the carboxyl (C=OOH) group.

Common posttranslational modifications include methylation of the ε-amino group, giving methyl-, dimethyl-, and trimethyllysine (the latter occurring in calmodulin); also acetylation, sumoylation, ubiquitination, and hydroxylation - producing the hydroxylysine in collagen and other proteins. O- Glycosylation of hydroxylysine residues in the endoplasmic reticulum or Golgi apparatus is used to mark certain proteins for secretion from the cell. In opsins like rhodopsin and the visual opsins (encoded by the genes OPN1SW, OPN1MW, and OPN1LW), retinaldehyde forms a Schiff base with a conserved lysine residue, and interaction of light with the retinylidene group causes signal transduction in color vision (See visual cycle for details). Deficiencies may cause blindness, as well as many other problems due to its ubiquitous presence in proteins.

Usage examples of "lysine".

These crystals were analyzed and it was reported that within each secretin molecule there existed 3 lysines, 2 arginines, 2 prolines, i histi-dine, i glutamic acid, i aspartic acid, and i methionine.

Since most of the abbreviations consist of the first three letters of the name, they are not difficult to memorize: glycine gly alanine ala valine val leucine leu asparagine asp'Ntb aspartic acid asp glutamine ghrNH2 glutamic acid glu THE HUMAN BRAIN isoleucine proline phenylalanine tyrosine tryptophan serine threonine ileu pro phe tyr try ser thr lysine histidine lys his arginine methionine arg met cystine cysteine cy-S-cy-SH Of the abbreviations that are more than the first three letters of the names, ileu, asp-NH2, and ghrNH2 should be clear.