The main difference between cystine and cysteine is that cystine is usually regarded as a semi-essential amino acid, whereas cysteine is a non-essential amino acid.
Amino acids are the structural units of proteins that are essential for the functional metabolisms of the body. It is vital to understand the structure and properties of amino acids in order to determine the protein structure and function. The human body needs 20 different amino acids. The body can produce only 10 amino acids, and the rest must be taken from food sources. The amino acids the body produces are non-essential amino acids, and those that the human body cannot produce within are essential amino acids. Cystine and cysteine are two such amino acids necessary for the body. These two types are interconvertible in the body. Both these amino acids contain sulfur. Despite their similarities, each of this amino acid is responsible for different tasks in the body.
Key Areas Covered
1. What is Cystine
– Definition, Formation, Features
2. What is Cysteine
– Definition, Formation, Features
3. Similarities Difference Cystine and Cysteine
– Outline of Common Features
4. Difference Between Cystine and Cysteine
– Comparison of Key Differences
Amino Acids, Cystine, Cysteine
What is Cystine
Cystine is a non-essential amino acid that can be produced in the human body. Cystine is formed by the oxidation of two cysteine molecules. This amino acid is a semi-essential amino acid. Moreover, it is abundant in the skeleton, connective tissues, and in hair.
Cystine is the least soluble and more stable than cysteine. Furthermore, it is essential to form glutathione, a natural antioxidant that removes toxins in the liver.
What is Cysteine
Cysteine is formed from the two amino acids: methionine and serine. Methionine provides the sulfur atom, while serine provides the carbon skeleton for cysteine. Cysteine is then converted to cystine by oxidation with the presence of cystine reductase enzyme. In fact, cysteine is important in many ways. It is unique from the rest of the amino acids due to the presence of the thiol group. This group can also undergo a redox reaction (oxidation/reduction). Thus, cysteine shows antioxidant properties.
The conversion of cysteine to pyruvate results in the formation of glucose. In fact, it is the most vital dietary source of sulfur for the body. Moreover, sulfur-containing compounds, including insulin, coenzyme-A, glutathione, and vasopressin, originate from cysteine. Although cysteine is a non-essential amino acid, it may be essential for infants and adults who show malabsorption syndromes.
Similarities Between Cystine and Cysteine
- Cystine and cysteine are two such amino acids necessary for the body.
- Both these amino acids also contain sulfur.
- Moreover, these two types are interconvertible in the body.
Difference Between Cystine and Cysteine
Cystine is a non-essential amino acid the human body produces, while cysteine is an amino acid containing methionine and serine.
Cystine is less soluble than cysteine, while cysteine is more soluble than cystine.
Cystine is more stable than cysteine.
Cystine is formed by the oxidation of cysteine, whereas cysteine is formed from the two amino acids: methionine and serine.
Cystine is a semi-essential (maybe essential) amino acid, while cysteine is a non-essential amino acid.
Moreover, cystine is not as easily absorbed by the body as cysteine.
In conclusion, cystine and cysteine are two such amino acids necessary for the body. However, the main difference between cystine and cysteine is that cystine is a semi-essential amino acid, whereas cysteine is a non-essential amino acid.
1. Naik, Prakash. Biochemistry. JP Medical, 2015.
2. “Cystine.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 2021.
1. “Cystine-3D-balls” By Ben Mills – Own work (Public Domain) via Commons Wikimedia
2. “L-cysteine-3D-balls2” By Photohound – Derivative work of User:Benjah-bmm27 (Public Domain) via Commons Wikimedia