Serine
- 2-amino- 3-hydroxy- propan-1- acid
- α -amino- β -hydroxypropionic acid
- Hydroxyalanine
- Abbreviations: Ser ( Three letter code)
- S ( single letter code )
- 56-45-1 (L -serine )
- 312-84-5 (D -serine )
- 302-84-1 (DL -serine )
White, needle-shaped, sweet-tasting crystals
Fixed
215-225 ° C
- PKCOOH: 2.21
- PKNH2: 9.15
- Well in water (360 g · l-1 at 20 ° C)
- Insoluble in diethyl ether and ethanol
Template: Infobox chemical / molecular formula search available
Serine, abbreviated Ser or S is a proteinogenic α - amino acid not essential in the L configuration [( S)-configuration ].
If in this text or in the scientific literature " serine " without further suffix (prefix ) is mentioned, L- serine is meant.
Occurrence
L- serine was first isolated from the silk gum, therefore, also the name derives (Latin sericum: silk).
Serine is also part of the Phosphoglyzerids phosphatidylserine, a block of biomembranes.
Stereochemistry
Serine has a stereogenic center and thus has two enantiomers, D-amino acid D -serine (Synonyms: (R ) -serine ) and its mirror image, the "natural" L -serine. The racemate DL -serine [ Synonym: ( RS)- serine ] consists of equal parts of L -serine and D -serine. When referred to in the scientific literature serine without any further addition is almost always meant L-serine.
L- serine racemization (partially) lighter than other proteinogenic L -amino acids. Therefore, many L-serine preparations contain small amounts ( 0.5 to 3% ) of D- serine.
Properties
Serine is at neutral pH mainly as a zwitterion before, the formation of which is explained by the fact that the proton of the carboxyl group migrates to the electron pair of the nitrogen atom of the amino group:
In an electric field, the zwitterion migrates not because it is not loaded as a whole. Strictly speaking, this is at the isoelectric point ( at a certain pH value) of the case in which the serine has its lowest solubility in water. The isoelectric point of serine is 5.68.
As well as all amino acids having a (hydrophilic) OH group ( hydroxy group ) may be phosphorylated serine and thus plays an important role in the activation or inactivation of enzymes. In addition, it is often located in the active site of enzymes and plays an important role for biocatalysis: Examples are the serine proteinases and their inhibitors, the serpins ( serine proteinases inhibitors).
Biosynthesis and degradation
For biosynthesis and degradation, including structural formulas, see section links.
By oxidation and subsequent transamination starting from 3 -phosphoglycerate serine is synthesized. Serine is degraded in the body to glycine, but it can be converted by the serine dehydratase to pyruvate in a PALP - dependent deamination eliminated.
Technical production
Industrial L- serine is produced by fermentation, in an estimated amount of 100-1000 tonnes per year. Alternatively, proteins containing keratin may be hydrolyzed with hydrochloric acid and neutralized with ammonia. The resulting mixture of 20 proteinogenic amino acids (one of which is the L- serine ) is separated due to different solubilities and by means of ion exchange chromatography. The individual fractions are further purified by recrystallization.
D-serine
In glial cells and neurons D -serine is formed by the enzyme serine racemase. At NMDA receptors D-serine acts as an endogenous co- agonist, it binds to the NR1 subunit and increases the affinity of this receptor to glutamate. There is evidence that a physiological deficiency of D -serine may play a role in depression events.