Pyridoxal-5'-phosphate monohydrate is a metabolite of vitamin B6 and is the most important coenzyme variant in the intracellular phosphorylation of vitamin B6, and can be interconverted with other variants including pyridoxal 5'-phosphate (PNP) and pyridoxal 5'-phosphate (PMP). It has the ability to modify lysine and valine residues in proteins and has properties that inhibit purinergic receptors and intracellular calcium influx. In addition, it is involved in a variety of biochemical reactions (e.g.: carbohydrate, protein, and fatty acid metabolism, etc.) and can modify peptides and impede their parent ion ionisation efficiency.