Pyridoxal 5’-Phosphate

Uses

Enzyme cofactor.Normal coenzyme form of Vitamin B6

Uses

Pyridoxal 5′-phosphate hydrate has also been used:

• as a reference standard to quantify vitamin B₆ in feed and digesta samples using high performance liquid chromatography (HPLC)
• in D-amino acid transaminase reaction(10)
• as a cofactor for L-glutamic acid decarboxylase

Definition

ChEBI: Pyridoxal 5'-phosphate is the monophosphate ester obtained by condensation of phosphoric acid with the primary hydroxy group of pyridoxal. It has a role as a coenzyme, a human metabolite, an Escherichia coli metabolite, a Saccharomyces cerevisiae metabolite, a mouse metabolite, an EC 2.7.7.7 (DNA-directed DNA polymerase) inhibitor and a cofactor. It is a vitamin B6 phosphate, a member of methylpyridines, a monohydroxypyridine and a pyridinecarbaldehyde. It is functionally related to a pyridoxal. It is a conjugate acid of a pyridoxal 5'-phosphate(2-).

General Description

Pyridoxal 5′-phosphate (PLP) is synthesized in a multiple-step process. The two pathways inlcude pyridoxal phosphate biosynthetic protein (PdxA)- pyridoxine-5′-phosphate synthase (PdxJ) pathway and the pyridoxal 5′-phosphate synthase subunit PDX1/PDX2 pathway. It is the active form of pyridoxine.

Biochem/physiol Actions

Pyridoxal 5′-phosphate (PLP) aids in carbohydrate and fat metabolism by serving as a cofactor. It is majorly responsible for catalyzing the enzymatic reactions involved in sphingolipid synthesis and neurotransmitter (dopamine and serotonin) synthesis. PLP is used in the studies of PLP-dependent enzyme active sites. PLP is also a cofactor for a wide range of enzymes including mitochondrial 5-Aminolevulinic acid synthase (ALAS) cysteine desulfurase, cystathionine γ-synthase (CGS), ornithine 4,5-aminomutase (OAM), and D-serine dehydratase.

Biotechnological Applications

Pyridoxal 5’-Phosphate(PLP) is also often employed as an inhibitor and site-directed, conformationally sensitive reporter group for studying the environment of reactive amino groups within proteins. PLP forms aldimine adducts that can be reduced with nucleophilic reducing reagents such as sodium borohydride or sodium cyanoborohydride. Solid PLP is light-sensitive, and solutions should be prepared fresh. There are four pKa values associated with this coenzyme: a pKa < 2.5 and another at 6.20 for the phosphate group, a pKa of 4.14 for the hydroxyl group, and a pKa of 8.69 for the pyridinium group.

Synthesis

A process for the synthesis ofpyridoxal5' -phosphate, comprising the steps of:
a) adding phenetidine into pyridoxal solution, and reacting to generate pyridoxal Schiff base;
b) adding pyridoxal Schiff base into ionic liquid, and stirring until the pyridoxal Schiff base is fully dissolved to obtain an ion mixed solution; adding pyridoxal Schiff base into ionic liquid, stirring at 35-45 ℃, and cooling the obtained ionic mixed solution to room temperature after the pyridoxal Schiff base is completely dissolved;
c) adding polyphosphoric acid into the ion mixed solution in which the pyridoxal Schiff base is dissolved, stirring for reaction, cooling after the reaction is finished, and separating out solids from the ion mixed solution; filtering solid particles separated out from the ion mixed solution, wherein the solid obtained by filtering is pyridoxal 5' -phosphate Schiff base, and the obtained liquid is phosphorus-containing ionic liquid; the weight ratio of pyridoxal Schiff base dissolved in the ion mixed solution to the polyphosphoric acid is within the range of 1:1-1:3, the reaction time is within the range of 8-12h, the reaction temperature is within the range of 25-40 ℃, and the temperature is reduced to 10 ℃ after the reaction is finished; the phosphorus-containing ionic liquid obtained by filtering can be recycled;
d) carrying out hydrolysis purification reaction on the pyridoxal 5 '-phosphate Schiff base obtained in the step c) to obtain a final product pyridoxal 5' -phosphate.

Enzyme inhibitor

This vitamin B6-derived coenzyme, often abbreviated PLP, plays a central role in metabolism.
In addition to facilitating aminotransfer reactions, PLP is a coenzyme in reactions involving:
(a) loss of the a-proton, resulting in racemization, cyclization, or b-elimination/replacement (e.g., alanine racemase, 1- aminocyclopropane-1-carboxylate synthase, and serine dehydratase, respectively);
(b) loss of the a-carboxylate as carbon dioxide (e.g., glutamate decarboxylase);
(c) removal/replacement of a group by aldol cleavage (e.g., threonine aldolase);
(d) catalysis via ketimine intermediates (e.g., selenocysteine lyase).