Keywords: Pyrroloquinoline quinone.svg Skeletal formula of pyrroloquinoline quinone PQQ cofactor Created using http //www acdlabs com/download/chemsk html ACD/ChemSketch 10 0 and Inkscape Own 2007-05-27 Fvasconcellos 21 57 27 May 2007 UTC Carboxylic acids Cofactors Ketones Nitrogen heterocycles |