Lysine
Essential amino acid crucial for protein synthesis and metabolism.
Lysine (symbol Lys or K; also L-lysine) is an α-amino acid that serves as a building block for many proteins. Its structure includes an α-amino group, an α-carboxylic acid group, and a side chain; at physiological pH in water, the amino group is protonated, the carboxyl group is deprotonated, and the side chain is partially protonated, giving lysine its classification as a basic, charged, aliphatic amino acid. It is encoded by the codons AAA and AAG. Like most amino acids, its α-carbon is chiral, and while lysine can refer to either enantiomer or a racemic mixture, the biologically active form is L-lysine, where the α-carbon is in the S configuration. The human body cannot synthesize lysine, making it an essential nutrient that must be obtained from the diet. In organisms that do synthesize lysine, two main biosynthetic pathways exist: the diaminopimelate pathway, found in prokaryotes and plants, and the α-aminoadipate pathway, found in yeast, fungi, and some protists. Lysine catabolism proceeds through several pathways, most commonly the saccharopine pathway. Beyond its role in protein synthesis, lysine is involved in collagen crosslinking, the uptake of essential minerals, and the production of carnitine, which is critical for fatty acid metabolism. It also participates in histone modifications, influencing the epigenome, and its ε-amino group frequently engages in hydrogen bonding and acts as a general base in catalysis. A deficiency in lysine can lead to defective connective tissues, impaired fatty acid metabolism, anemia, and systemic protein-energy deficiency, while an excess due to ineffective catabolism can cause severe neurological disorders. Lysine was first isolated in 1889 by German chemist Ferdinand Heinrich Edmund Drechsel from the hydrolysis of the protein casein, and its chemical structure was determined by Emil Fischer and Fritz Weigert in 1902. The one-letter symbol K was assigned because it is alphabetically nearest to L, which was already assigned to leucine.
- discovered_by
- Ferdinand Heinrich Edmund Drechsel
- structure_determined_by
- Emil Fischer and Fritz Weigert
- classification
- Basic, charged, aliphatic α-amino acid
- biological_role
- Proteinogenesis, collagen crosslinking, mineral uptake, carnitine production, histone modifications
Lore & Background
Lysine is an α-amino acid that serves as a building block for many proteins. It features an α-amino group, an α-carboxylic acid group, and a side chain, all of which exist in specific charged states when dissolved in water at physiological pH, classifying it as a basic, charged, aliphatic amino acid. The α-carbon is chiral, and while lysine can refer to either enantiomer or a racemic mixture, the biologically active form for this entry is the enantiomer with the α-carbon in the S configuration. It is encoded by the codons AAA and AAG. In terms of range, lysine is essential for humans, meaning the body cannot synthesize it and it must be obtained from the diet. In organisms that do synthesize it, two main biosynthetic pathways exist: the diaminopimelate pathway, found in prokaryotes and plants, and the α-aminoadipate pathway, present in yeast, protists, and higher fungi. Lysine plays several roles in humans, including proteinogenesis, crosslinking of collagen polypeptides, uptake of essential mineral nutrients, and production of carnitine for fatty acid metabolism. It is also involved in histone modifications, impacting the epigenome. The ε-amino group of lysine often participates in hydrogen bonding and acts as a general base in catalysis. A lack of lysine can lead to disease states such as defective connective tissues, impaired fatty acid metabolism, anaemia, and systemic protein-energy deficiency, while an overabundance from ineffective catabolism can cause severe neurological disorders. Lysine was first isolated in 1889 by German biological chemist Ferdinand Heinrich Edmund Drechsel from the hydrolysis of the protein casein, and its chemical structure was determined by Emil Fischer and Fritz Weigert in 1902.
Reader's Guide
Lysine is essential in humans and must be obtained from the diet, as the human body cannot synthesize it. It plays several roles, most importantly in proteinogenesis, but also in the crosslinking of collagen polypeptides, uptake of essential mineral nutrients, and in the production of carnitine, which is key in fatty acid metabolism. Lysine is also often involved in histone modifications, impacting the epigenome. A lack of lysine can lead to defective connective tissues, impaired fatty acid metabolism, anaemia, and systemic protein-energy deficiency. Conversely, an overabundance of lysine, caused by ineffective catabolism, can cause severe neurological disorders. Two main biosynthetic pathways exist in organisms that synthesize lysine: the diaminopimelate pathway and the α-aminoadipate pathway. Catabolism primarily occurs through the saccharopine pathway, which is the reverse of the α-aminoadipate biosynthesis pathway.
Did You Know?
- The one-letter symbol K was assigned to lysine because it is the only letter not already used for another amino acid that is phonetically reminiscent of 'lysine'.
- Lysine contains an ε-ammonium group attached to the fifth carbon (the ε-carbon) from the α-carbon.
- The human body cannot synthesize lysine; it is essential and must be obtained from the diet.
Frequently Asked Questions
What is Lysine?
Lysine (symbol Lys or K) is a basic, aliphatic α-amino acid that carries a positive charge under physiological conditions. It serves as a fundamental building block for a wide variety of proteins in living cells.
Why is Lysine considered an essential amino acid?
Human cells lack the enzymatic pathway needed to build lysine from scratch, so it must be supplied through the diet. Without adequate dietary intake, protein synthesis and downstream metabolic processes are compromised.
What are Lysine's key biological roles beyond protein synthesis?
Lysine participates in collagen crosslinking, mineral uptake, carnitine biosynthesis, and histone modifications. It also acts as a precursor for several other biologically active molecules.
Who discovered Lysine and who determined its structure?
The amino acid was first isolated and identified by Ferdinand Heinrich Edmund Drechsel. Its full chemical structure was subsequently elucidated by Emil Fischer and Fritz Weigert.
Which codons encode Lysine in the genetic code?
Lysine is specified by two codons, AAA and AAG, in the standard genetic code. During translation, either of these codons directs the ribosome to attach a lysine residue to the growing polypeptide chain.
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