 Indole-3-pyruvic acid

Indole-3-pyruvic acid is an indole-substituted oxo carboxylic acid, systematically 3-(1H-indol-3-yl)-2-oxopropanoic acid. Its neutral molecular formula is ${\mathrm{C}}_{11}{\mathrm{H}}_9\mathrm{N}{\mathrm{O}}_3$. Its conjugate base is indole-3-pyruvate, which retains the same carbon skeleton after loss of a proton.^[ref]

The acid/base relationship can be represented asBoth sides have eleven carbon atoms and three oxygen atoms; the change concerns protonation and charge. This is different from the biochemical conversion of indole-3-pyruvate to indole-3-acetate, which releases carbon dioxide and changes the carbon inventory of the organic product.^[ref]

An illuminating comparison is therefore between changing a solution's acid/base conditions and changing a metabolite's carbon skeleton. Those operations can alter names or measured signals for different reasons. Identifying the chemical structure and protonation state prevents the acid, its anion and the shorter-side-chain auxin product from being treated as one interchangeable chemical identity.