L-Lysine hydrochloride, 98.0+%

Lysine (abbreviated as Lys or K), encoded by the codons AAA and AAG) is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated -+NH3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated –COO- form under biological conditions), and a side chain lysyl ((CH2)4NH2), 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 (NH3+) 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, retinaldehyde forms a Schiff base with a conserved lysine residue, and interaction of light with the retinylidene group causes signal transduction in color vision. Deficiencies may cause blindness, as well as many other problems due to its ubiquitous presence in proteins.