Lipidketts

Lipidketts are a hypothetical class of lipid-derived ketone-containing metabolites proposed to describe certain ketone-bearing lipids that arise in some microorganisms and algae under nutrient stress. They consist of a glycerol or sphingoid backbone linked to long hydrocarbon chains and bear one or more ketone functional groups, typically at the beta or gamma position. The usual chain lengths range from 14 to 28 carbon atoms, and some members carry methyl branches.

The term lipidkett was coined to describe this ketone-bearing lipid family after initial characterizations in extremophile bacteria. Since then, several structural variants have been cataloged, including mono-ketone and di-ketone species, with varying degrees of unsaturation.

Biosynthesis appears to involve acyl-CoA precursors funneled into specialized enzymes termed lipidkett synthases, which introduce or preserve ketone functionality during lipid remodeling. Pathways intersect traditional beta-oxidation and peroxisomal-like cycles in some organisms, and production is upregulated under carbon limitation or oxidative stress.

Proposed functions include serving as energy reserves when carbohydrate supply is low, contributing to membrane remodeling in stressed cells, and acting as signaling lipids that influence gene expression and biofilm behavior. Their exact biological roles remain under investigation, and they may participate in interspecies interactions.

Analytical detection relies on liquid chromatography–mass spectrometry and gas chromatography–mass spectrometry, often after derivatization to stabilize the ketone group. Given the novelty of the field, reference standards are limited and identifications are typically based on MS/MS spectra and retention times. Ongoing research aims to clarify distribution, biosynthetic routes, and physiological significance. See also: lipid metabolism, ketone bodies, lipid signaling.