Pyridoxal (PL) isVitamin B6One of the components of Pyridoxine is aldehyde obtained by oxidizing pyridoxine.Its chemical formula is 3-hydroxy-5-hydroxymethyl-2-methylPyridine-4-formaldehyde。
Chinese name
Pyridoxal
Foreign name
pyridoxal，PL
Nature
Unstable in neutral and alkaline, prone to photolysis
Discovery
In 1942, it was found in the extract of viscera
CAS No
66-72-8
Molecular formula
CeightHnineNOthree
molecular weight
one hundred and sixty-seven point one six two zero zero
Precision quality
one hundred and sixty-seven point zero five eight zero zero
It is unstable in neutral and alkaline, and prone to photolysis.It has an effect on the growth of Streptococcus lactisPyridoxineIt is thousands of times larger. As a substance to restore the function of tyrosine deaminase, it was discovered from the extracts of organs in 1942.The function in organism is to formPyridoxal phosphate。It has many coenzyme functions.[1]
In vivo transformation
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Vitamin B6Pyridoxal, pyridoxine and pyridoxamine are three kinds of vitamins with the same effect in food. They are all converted from the liver of mammals to their activated form pyridoxal phosphate.Vitamin B6 exists in many foods, but the lack of vitamin B6 is much wider than people think.No disease is associated with vitamin B6 deficiency, but convulsion symptoms have been observed in infants fed food with insufficient vitamin B6.Pyridoxal phosphate is a cofactor in many different types of enzymatic reactions, including transaminase and diamine oxidase reactions, histidine to histamine reactions, serine to pyruvate reactions, and many reactions in tryptophan catabolism.The status of pyridoxal can be evaluated by pyridoxal phosphate and its related transaminase activity.The transaminase activity was determined before and after adding pyridoxal to the sample.The reaction principle of transaminase can be illustrated by the transamination of alanine into pyruvate as an example.[1]
ATP: pyridoxal 5-phosphate transferase (E.C.2.7.1.35), usually called pyridoxal kinase.This is a kinase reaction and generates ADP at the same time.Pyridoxine is the primary alcohol derivative of pyridoxal, which can also be used as the substrate of the reaction.Then, the alcohol group is oxidized to aldehyde to form pyridoxal phosphate.Pyridoxine can also be the substrate of the reaction.
(2) Pyridoxal phosphate+L-alanine ←→ Schiff base
Alanine and pyridoxal phosphate form a Schiff base between their amino and aldehyde groups, which is the first reaction in a series of reversible reactions.
(3) Schiff's base H Pyridoxine phosphate ←→ Pyruvate
Schiff's base breaks the N-C bond of its alanine part by adding a water molecule to the bond, so as to release pyruvate and pyridoxamine phosphate.
(4) Oral ketoglutaric acid+pyridoxamine phosphate ←→ Schiff base
The carbonyl group of ketoglutaric acid and the amino group of pyridoxamine phosphate are condensed to form Schiff's base.
Schiff's base is disconnected due to the N-C bond of the pyridoxamine phosphate part, where a molecule of water is added, thus releasing L-glutamic acid and pyridoxal phosphate.Pyridoxal phosphate can be added back into the cycle.[1]
Catalysis of pyridoxal
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It is well known that pyridoxal（Vitamin B6）The catalytic reaction can be carried out via Schiff base and its tautomeric formula (3.106) (Metzler et al., 1954).Pyridoxal dependent enzymes can catalyze a variety of amino acid reactions, such as decarboxylation, elimination, and transamination.Although these reaction mechanisms have been studied, their influence on organic chemistry is quite limited.For example, Llor and Cortijo (1977) pointed out that the tautomerism between (3.105) and (3.106) can be used to determine the polarity of solvents. The maximum absorption of these two tautomers is different (415335nm respectively), and their relative strength changes with the size of solvent polarity.They proved that there is a linear relationship between the equilibrium △ G and the z value of Kosower.This model is a particularly useful method for determining the polarity of the active site of pyridoxal coase.[2]
Another important pyridoxal transfer reaction is decarboxylation. As mentioned earlier, this reaction is highly dependent on the reaction medium.Therefore, in order to simulate the catalytic effect of decarboxylase, the solvation of carboxyl groups must be considered.It has been reported that the decarboxylation of amino acids delivered by H pyridoxal needs to be carried out under rather intense conditions (100oC. 4h), but there is no example of model reaction under environmental conditions.[1]
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In the 19th century, pelagra was found to be caused by the lack of nicotinic acid, and another disease was found in 1926vitaminWhen the feed is deficient, it will also cause small mice to induce pellagra. Later, this substance was namedVitamin B6It was not isolated until 1938-1939, and vitamin B6 was qualitatively synthesized.[2]
Food source
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Pyridoxal has a wide range of food sources, including animal and plant foods.Generally, meat, whole grain products (especially wheat), vegetables and nuts are high in content.The bioavailability of pyridoxal in food from animal sources is better than that of food from plant sources.The content of yeast powder is the most in animal and plant foods, and there is also a lot of rice bran or white rice, followed by meat, poultry, fish, potatoes, sweet potatoes and vegetables.
Each 100g edible part of various foods containsvitaminThe amount of B6 is as follows: yeast powder 3.67mg, defatted rice bran 2.91mg, white rice 2.79mg, flax meal 1.25mg, cheese 0.8-0.04mg, carrot 0.7mg, fish 0.45mg, whole wheat extract 0.4-0.7mg, meat 0.3-0.08mg, milk 0.3-0.03mg, egg 0.25mg,Spinach0.22mg, sweet potato 0.14-0.23mg, pea 0.16mg, soybean 0.1mg, orange 0.05mg.[1]
