Lysine
Lysine — An essential amino acid (Lys, K) with a positively charged side chain at physiological pH, frequently involved in post-translational modifications.
What Is Lysine?
Lysine (Lys, K) is a positively charged amino acid with a primary amine side chain (-CH2CH2CH2CH2NH2, pKa ~10.5, MW: 146.19 Da). Its epsilon-amino group is the most common target for bioconjugation reactions (NHS esters, isothiocyanates) and post-translational modifications (acetylation, methylation, ubiquitination).
Roles in Peptide Research
- Conjugation site: NHS ester chemistry targets lysine amines for fluorescent labeling, PEGylation, and drug conjugation
- Lipidation: Semaglutide uses a C18 fatty acid conjugated through a lysine side chain for albumin binding
- Lactam bridges: Lys-Asp/Glu side-chain cyclization creates lactam-bridged cyclic peptides
- Tryptic cleavage: Trypsin cleaves after Lys and Arg, making these residues determinants of proteolytic half-life
Frequently Asked Questions
What is Lysine?
An essential amino acid (Lys, K) with a positively charged side chain at physiological pH, frequently involved in post-translational modifications.
Why is Lysine important in peptide research?
Lysine is a fundamental concept in amino acid as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.