====== Lysine ======
 

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 [[protein]]s. 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.
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[[Acetylated lysine 174]]