Serine
| Serine | |
|---|---|
 
| |
| Systematic name | (S)-2-amino-3-hydroxypropanoic acid |
| Abbreviations | Ser S |
| Chemical formula | C3H7NO3 |
| Molecular mass | 105.09 g mol-1 |
| Melting point | 228 °C |
| Density | 1.537 g cm-3 |
| Isoelectric point | 5.68 |
| pKa | 2.13 9.05 |
| CAS number | [56-45-1] |
| PubChem | 5951 |
| EINECS number | 200-274-3 |
| SMILES | N[C@@H](CO)C(O)=O |
| Disclaimer and references | |
Serine is an α-amino acid that is common in many proteins, sometimes in substantial concentrations in the outer regions of soluble proteins due to its hydrophilic nature. Serine is an important component of phospholipids and participates in the biosynthesis of purines and pyriminidines. With an easily removed hydrogen on the hydroxyl side chain, serine is often a hydrogen donor in enyzmes, such as trypsin and chymotrypsin, playing an important role in the function as catalysts.
In humans, the L-isomer, which is the only form that is involved in protein synthesis, is one of the 20 standard amino acids required for normal functioning. However, it is considered to be a "non-essential" amino acid since it does not have to be taken in with the diet, but can be synthesized by the human body from other compounds through chemical reactions.
Serine's three letter code is Ser, its one letter code is S, its codons are AGU and AGC, and its systematic name is 2-Amino-3-hydroxypropanoic acid (IUPAC-IUB 1983). The name serine was derived from the Latin for silk, "sericum," since serine was first isolated from silk protein. While the amino acids glycine and alanine make up the bulk of silk protein, it is also a rich source of serine.
Structure
In biochemistry, the term amino acid is frequently used to refer specifically to alpha amino acids: those amino acids in which the amino and carboxylate groups are attached to the same carbon, the so-called α–carbon (alpha carbon). The general structure of these alpha amino acids is:
R
|
H2N-C-COOH
|
H
where R represents a side chain specific to each amino acid.
Most amino acids occur in two possible optical isomers, called D and L. The L amino acids represent the vast majority of amino acids found in proteins. They are called proteinogenic amino acids. As the name "proteinogenic" (literally, protein building) suggests, these amino acid are encoded by the standard genetic code and participate in the process of protein synthesis. In serine, only the L-stereoisomer is involved in synthesis of mammalian proteins.
Serine has the chemical formula HO-CH2-CH(NH2)-COOH (alternatively, HO2C-CH(NH2)-CH2-OH), or more generally, C3H7NO3.
Serine, like threonine, has a short group ended with a hydroxyl group. The hydroxyl group attached makes it a polar amino acid. Its hydrogen is easy to remove, so serine and threonine often act as hydrogen donors in enzymes. Both are very hydrophilic, therefore the outer regions of soluble proteins tend to be rich with them.
Biosynthesis
Serine is not essential to the human diet, since it is synthesized in the body. The synthesis of serine starts with the oxidation of 3-phosphoglycerate forming 3-phosphohydroxypyruvate and NADH. Reductive amination of this ketone followed by hydrolysis yields serine.
Serine also gives rise to the amino acid glycine, thus glycine is not classified as an essential amino acid. The enzyme serine hydroxymethyl transferase catalyzes this reversible, simultaneous conversions of L-serine to glycine (retro-aldol cleavage) and 5,6,7,8-tetrahydrofolate to 5,10-methylenetetrahydrofolate (hydrolysis) (Lehninger 2000). The conversion of serine to glycine is characterized as follows:
- HO2C-CH(NH2)-CH2-OH (serine) + H2folate → HO2CCH2NH2 (glycine) + CH2-folate + H2O
Function
Metabolic
Serine is important in metabolism in that it participates in the biosynthesis of purines and pyrimidines. It is also the precursor to several amino acids, including glycine, cysteine, tryptophan (in bacteria). It is also the precursor to numerous of other metabolites, including sphingolipids. Serine is also a precursor to folate which is the principal donor of one carbon fragments in biosynthesis.
Structural
Serine plays an important role in the catalytic function of many enzymes. It has been shown to occur in the active sites of chymotrypsin, trypsin, and many other enzymes. The so-called nerve gases and many substances used in insecticides have been shown to act by combining with a residue of serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Without the esterase activity that usually destroys acetylcholine as soon as it performs its function, dangerously high levels of this neurotransmitter build up, quickly resulting in convulsions and death.
As a constituent (residue) of proteins, its side chain can undergo O-linked glycosylation. This might be important in explaining some of the devastating consequences of diabetes. It is one of three amino acid residues that are commonly phosphorylated by kinases during cell signaling in eukaryotes. Phosphorylated serine residues are often referred to as phosphoserine. Serine proteases are a common type of protease.
Signaling
D-serine, synthesized by serine racemase from L-serine, serves as a neuronal signaling molecule by activating NMDA receptors in the brain.
Chemical Synthesis
Serine is prepared from methyl acrylate.[1]
See also
- Serine aggregation properties in Serine octamer clusters
ReferencesISBN links support NWE through referral fees
- ↑ Carter, H. E.; West, H. D. “dl-Serine” Organic Syntheses, Collected Volume 3, p.774 (1955). http://www.orgsyn.org/orgsyn/pdfs/CV3P0774.pdf
External links
Template:ChemicalSources
| Major families of biochemicals | ||
| Peptides | Amino acids | Nucleic acids | Carbohydrates | Nucleotide sugars | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides | ||
| Analogues of nucleic acids: | The 20 Common Amino Acids | Analogues of nucleic acids: |
| Alanine (dp) | Arginine (dp) | Asparagine (dp) | Aspartic acid (dp) | Cysteine (dp) | Glutamic acid (dp) | Glutamine (dp) | Glycine (dp) | Histidine (dp) | Isoleucine (dp) | Leucine (dp) | Lysine (dp) | Methionine (dp) | Phenylalanine (dp) | Proline (dp) | Serine (dp) | Threonine (dp) | Tryptophan (dp) | Tyrosine (dp) | Valine (dp) | ||
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