Pyridoxal phosphate

• (4- formyl -5-hydroxy -6- methylpyridin-3 -yl) methyldihydrogenphosphat
• Codecarboxylase
• Pyridoxal -5-phosphate

• 54-47-7
• 41468-25-1 (monohydrate)
• 853645-22-4 ( hydrate)

Light yellow solid

Fixed

140-143 ° C

Hydrate

Template: Infobox chemical / molecular formula search available

Pyridoxal phosphate ( PLP short or PALP, P5P ) is one of the most important cofactors in the animal organism. Under physiological conditions, the phosphate group is deprotonated and doubly negatively charged before. PLP is involved in various reactions of the amino acids:

• Transamination
• Decarboxylation
• Dehydration

As well as the breakdown of glycogen.

Pyridoxal phosphate is the active form of pyridoxine (vitamin B6).

Role in transamination

In the transamination an amino group of an amino acid to a keto acid, a b is transmitted. The amino group is virtually exchanged; it arises from the keto acid is an amino acid and the "donor - amino acid" remains as a keto acid.

Pyridoxal phosphate assumes the role of " messenger ", ie transports the amino group from a to b. To the amino group is temporarily bonded to the PLP, that is, in this form, pyridoxamine phosphate. It lies in a complex bound to the specific enzyme before.

While interacting with the amino acid or with the PLP keto forms with its reaction partner is a so-called Schiff base ( aldimine ). It is stabilized by a positively charged group of the enzyme. Now it is through the N of the pyridine group, for intramolecular charge transfer and Ketiminformation. In this case, a bond is loosened, depending on the operation on the α - C atom of the amino acid.

There occur transamination and α - or β - eliminations.

Role in the elimination

Pyridoxal phosphate is also here initially a Schiff's base with the amino group of an amino acid such as cysteine. A charge transfer here leads to a loosening of the bond between the α - carbon atom and hydrogen. The SH group on the α - carbon atom is cleaved with this proton as hydrogen sulfide. It is now reactive to hydrolysis of the Schiff base between the amino acid and pyridoxal phosphate. The case split Aminopropensäure rearranges to Iminopropansäure and reacts with the release of ammonia to pyruvic acid.

Finding such eliminations for cysteine ​​, threonine and serine instead. Furthermore, there are β, γ -elimination in individual learning, there to homoserine and homocysteine.