Aconitic acid refers to organic compounds with the formula HO2CCH2C(CO2H)=CHCO2H. A white solid, it is classified as a tricarboxylic acid. The two isomers are cis-aconitic acid and trans-aconitic acid. The conjugate base of cis-aconitic acid, cis-aconitate is an intermediate in the isomerization of citrate to isocitrate in the citric acid cycle. It is acted upon by the enzyme aconitase.