= Pyridoxamine phosphate
<Pyridoxamine phosphate> usually denotes pyridoxamine 5'-phosphate, the phosphate <ester> of the position-5 hydroxymethyl group of <pyridoxamine>. Its neutral-form <molecular formula> is $\mathrm{C_8H_{13}N_2O_5P}$. It is an active <Vitamin B6> <coenzyme> form, chemically distinct from both free pyridoxamine and <pyridoxal phosphate>.<Pyridoxamine phosphate in ChEBI>[CHEBI:18335, Definition, Formula and structure]{ref}<Vitamin B6 Fact Sheet for Health Professionals by the Office of Dietary Supplements>[Introduction, active PLP and PMP coenzyme forms]{ref}
A concrete reaction distinguishes the two phosphorylated forms. <Pyridoxal 5'-phosphate synthase> can oxidatively convert <pyridoxamine phosphate> into <pyridoxal phosphate>, producing <Ammonia> and <hydrogen peroxide> while consuming water and oxygen.<Pyridoxal 5'-phosphate synthase in IUBMB Enzyme Nomenclature>[EC 1.4.3.5, reaction 1]{ref} The transformation changes the aminomethyl group into an aldehyde group while retaining the phosphate ester.
For an ideal $1\,\mathrm{\mu mol}$ conversion by this reaction, one micromole each of <Ammonia> and <hydrogen peroxide> is produced. A peroxide assay can consequently report a coupled reaction signal, but identifying the B6 product remains a separate analytical question. A peroxide-producing impurity could mimic that signal without making the intended coenzyme.
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