Lysine definition structure formula and functions
Herpes disease is caused by herpes virus and can be cured by the drugs containing lysine. Lysine is an essential amino acid for the human body. Lysine is not only used in the treatment of herpes but for various other diseases as well. It also has many culinary applications. In this article we will discuss chemical aspects of lysine, its structure, sources and uses.
What is Lysine?
Lysine is an essential -amino acid which is found in many foods as protein. Its symbol is Lys or K. As we know amino acids are the basic structural units of protein, so Lysine is used in the synthesis of proteins. As it is an \[\alpha\] – amino acid so, it contains \[\alpha\] – amine group and \[\alpha\] – carboxylic acid group. We will discuss its structure in detail in the next section.
It is essential for our body, but our body cannot synthesize it on its own. So, it must be obtained from foods. Lysine helps in animal growth as well. That’s why Lysine supplements are used as animal feed, specially for chickens and pigs for their optimal growth and production of meat. Some plants and bacteria can synthesize lysine from aspartic acid which is also an amino acid. It is synthesized in organisms by mainly following two biosynthetic pathways –
Diaminopimelate pathway
\[\alpha\]– aminoadipate pathway
It was 1st isolated in 1889 by German Chemist Ferdinand Heinrich Edmund Drechsel from the casein phosphoprotein present in milk. Ferdinand Heinrich named lysine as ‘Lysin’. After almost thirteen years of its discovery and isolation, lysine was synthesized in 1902 by German Chemists Emil Fischer and Fritz Weigert. They determined the structure of the lysine as well.
As lysine is vital for many biological processes so its deficiency can cause many diseases such as anaemia, defects in tissues, protein energy deficiency etc. It is a vital organic compound for growth of plants and animals as well. Thus, lysine is an important – amino acid for various processes occurring in human beings, animals and plants as well.
Structure of Lysine
Lysine contains \[\alpha\] – amine group (In form of protonated -NH3+), \[\alpha\] – carboxylic acid group (In form of deprotonated -COO-), and a lysyl side chain [(CH2)4NH2] in its carbon chain. It is a covalent organic compound. It is encoded by the genetic codes AAA and AAG. It has a chiral \[\alpha\] – carbon. Its enantiomer L – Lysine in which \[\alpha\] – carbon is in the S configuration and is biologically active.
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Amino Acid Structure
\[\alpha\] – Carbon, amino group and carboxylic acid group are the backbone of lysine. Its chemical formula is C6H14N2O2. It is a linear amino acid molecule. Lysine is a base and water soluble. It forms hydrogen bonds with other molecules. Its structure formula L-lysine is given below –
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Structure of L- Lysine
General Structure of lysine –
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Foods Rich in Lysine or Sources of Lysine
Lysine is essential for proper growth and is used in biosynthesis of protein. As you know, lysine cannot be synthesized by our body and we must take it through diet. So, it becomes necessary for us to include lysine rich foods in our diet. As lysine is used in biosynthesis of proteins, so it naturally occurs in protein rich food items.
Meat (red meat), eggs, rajma, chickpeas, few species of fishes, soybeans, tofu, fenugreek seeds, cheese, pork, chicken etc. are good sources of lysine. Other beans, dairy products and Brewer’s yeast, mushroom also contain lysine.
Apart from these natural sources of lysine various other lysine supplements are also available. It is available in the form of tablets, capsules, creams and liquid solution form.
Function of Lysine
Lysine is necessary for the healthy functioning of the human body and some organisms, plants and animals. Catabolism of lysine takes place in the liver. Amino acids of lysine provide glucose to the human body through metabolism. It is metabolized into acetyl – CoA which forms adenosine triphosphate. Adenosine triphosphate is the currency of energy in our body. Lysine plays a vital role in the citric cycle in animals.
Allysine is a derivative of lysine which is used to produce collagen and elastin. These are essential for skin, joints etc.
Uses of Lysine
Lysine plays an important role in many biological processes. Its most common role is proteinogenesis. It is a base of protein structure. It is considered as amphipathic which means it shows both hydrophilic and lipophilic properties. Because of this it becomes even more important for various processes. Its amino group forms hydrogen bonds, covalent bonds and salt bridges with other molecules. Therefore, lysine contributes to protein stability as well. Lysine plays a major role in epigenetic regulation. Many histone modifications involve lysine. These modifications can affect gene regulation.
Lysine plays a key role in calcium homeostasis and fatty acid metabolism. It is involved in the crosslinking of helical polypeptides in collagen. It is a precursor for carnitine. Carnitine transports fatty acids to the mitochondria.
Lysine is useful in treatment of herpes. Herpes is caused by herpes simplex virus. Arginine promotes the growth of herpes simplex virus and lysine blocks the activity of arginine.
It helps the body to absorb calcium. As calcium is a must for healthy bones. So, researches show that lysine helps in prevention of osteoporosis.
Sometimes athletes take lysine supplements as protein supplements as studies show that lysine helps muscles to recover faster after stress.
Lysine is used as animal feed as it helps in their optimal growth. Thus, lysine is a key ingredient of food, which is used in poultry farms, pig farming etc. to feed chickens, pigs and other animals for their optimal growth and high - quality meat.
Early studies show that lysine is effective in treatment of canker sores and diabetes. Studies state that it can even prevent canker sores and diabetes. It reduces the blood sugar level. Lysine is helpful in reducing the stress as well.
A derivative of lysine is used in pain management as it serves as an anti – inflammatory agent. It can be helpful in preventing cardiovascular diseases and blood pressure fluctuations.
Deficiency of Lysine
As lysine plays key roles in many biological processes and essential for our body, so its deficiency causes various diseases also. Most of the diseases due to lysine are the result of downstream processing of lysine. Lack of lysine causes disease related to connective tissues. Lack of lysine may cause lack of carnitine levels in the body which may cause many health - related issues as carnitine transfers fatty acids to mitochondria and mitochondria is known as powerhouse of the cells. Deficiency of lysine may cause anaemia, protein energy malnutrition, neurological disabilities, epilepsy, ataxia and psychomotor impairment.
This ends our coverage on the topic “Lysine”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions of NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.
FAQs on Lysine Structure Properties and Biological Role
1. What is lysine in chemistry?
**Lysine is an essential α-amino acid with the molecular formula C6H14N2O2.** It contains an amino group (–NH2), a carboxyl group (–COOH), and a basic side chain with an additional –NH2 group. In biochemical terms, lysine is classified as a basic amino acid because its side chain can accept a proton. It is one of the 20 standard amino acids used in protein synthesis.
2. What is the structure of lysine?
**The structure of lysine consists of an α-carbon bonded to –NH2, –COOH, –H, and a side chain –(CH2)4NH2.** Its condensed structural formula is H2N–CH(COOH)–(CH2)4NH2. Key structural features include:
- An α-amino group
- An α-carboxyl group
- A long aliphatic side chain ending in a second amino group
This extra amino group makes lysine positively charged under physiological pH conditions.
3. Why is lysine classified as a basic amino acid?
**Lysine is classified as a basic amino acid because its side chain contains an additional amino group that can accept a proton (H+).** The terminal –NH2 group in the side chain becomes –NH3+ in aqueous solution. This gives lysine:
- A positive charge at physiological pH (~7.4)
- The ability to participate in ionic bonding and salt bridge formation in proteins
Its basicity arises from the presence of nitrogen atoms with lone pairs that can bind H+.
4. What is the zwitterion form of lysine?
**The zwitterion form of lysine is the structure in which it contains both positive and negative charges but is overall electrically neutral.** In aqueous solution near its isoelectric point, lysine exists as:
- α-amino group: –NH3+
- Carboxyl group: –COO−
- Side chain amino group: –NH3+
Because lysine has two amino groups and one carboxyl group, its charge state depends strongly on pH, which is a key concept in amino acid acid–base chemistry.
5. What is the isoelectric point (pI) of lysine?
**The isoelectric point (pI) of lysine is approximately 9.7.** The pI is the pH at which the amino acid has no net electrical charge. For lysine:
- It has three ionizable groups (–COOH and two –NH3+)
- The pI is calculated by averaging the two highest pKa values (those of the amino groups)
Because lysine is a basic amino acid, its pI is greater than 7.
6. How does lysine form peptide bonds?
**Lysine forms peptide bonds when its α-amino group reacts with the carboxyl group of another amino acid in a condensation reaction.** The reaction involves:
- Removal of H from –NH2
- Removal of OH from –COOH
- Formation of a peptide bond (–CO–NH–) and release of H2O
General reaction: Amino acid 1 + Amino acid 2 → Dipeptide + H2O. Lysine can also use its side-chain amino group in certain cross-linking reactions in proteins.
7. What is the difference between lysine and leucine?
**The main difference between lysine and leucine is that lysine is basic and positively charged, while leucine is nonpolar and hydrophobic.** Key differences include:
- Lysine: Side chain –(CH2)4NH2, polar and basic
- Leucine: Side chain –CH2–CH(CH3)2, nonpolar and aliphatic
- Lysine participates in ionic interactions; leucine stabilizes proteins via hydrophobic interactions
This difference affects protein folding and biochemical behavior.
8. What is the molar mass of lysine?
**The molar mass of lysine (C6H14N2O2) is approximately 146.19 g·mol−1.** It is calculated as:
- 6 × 12.01 (C) = 72.06
- 14 × 1.008 (H) = 14.11
- 2 × 14.01 (N) = 28.02
- 2 × 16.00 (O) = 32.00
Total ≈ 146.19 g·mol−1, which is used in stoichiometric and biochemical calculations.
9. How does pH affect the charge of lysine?
**The charge of lysine changes with pH because its amino and carboxyl groups can gain or lose protons (H+).**
- At low pH: fully protonated, overall positive charge
- At pH ≈ 9.7 (pI): net charge = 0
- At high pH: amino groups lose H+, overall negative charge
This acid–base behavior is essential in buffer systems, electrophoresis, and protein chemistry.
10. What are the chemical properties of lysine?
**Lysine exhibits basicity, amphoteric behavior, peptide bond formation, and salt formation due to its amino and carboxyl functional groups.** Its main chemical properties include:
- Amphoteric nature (acts as both acid and base)
- Formation of zwitterions in aqueous solution
- Ability to form peptide bonds in proteins
- Formation of salts with acids (e.g., lysine hydrochloride)
These properties make lysine important in amino acid chemistry, biochemistry, and protein structure studies.
