cisaconitate

Cis-aconitate, also known as cis-aconitic acid, is a short-lived intermediate in the citric acid cycle. It is the cis geometric isomer of aconitic acid and forms during the isomerization of citrate to isocitrate catalyzed by the enzyme aconitase.

In the mitochondrion, citrate is dehydrated by aconitase to form cis-aconitate, which is then hydrated to produce isocitrate. The overall process is reversible, allowing the interconversion of citrate, cis-aconitate, and isocitrate as metabolic conditions require. The enzyme’s active site and its iron-sulfur cluster facilitate the dehydration and hydration steps and help stabilize the intermediate.

Chemically, cis-aconitate contains a double bond adjacent to carboxylate groups; the designation "cis" refers to the configuration around that double bond. In physiological conditions, cis-aconitate typically exists only transiently and is often bound within aconitase during turnover rather than accumulating as a free metabolite in significant amounts.

Biological significance: The conversion of citrate to isocitrate via cis-aconitate is a necessary step in the citric acid cycle, supplying reducing equivalents and carbon skeletons for energy production and biosynthesis. Disruptions in aconitase activity can impair this step and affect cellular metabolism.

See also: citrate, aconitase, isocitrate, citric acid cycle.