Higher aliphatic 2,4-diketones: a ubiquitous lipid class with chelating properties, in search of a physiological function.

A group of homologous 2,4-diketones with chain lengths from C13 to C25, derived from fatty acids, is present in human and mammalian tissues and urine. The presence of this lipid class, members of which possess marked chelating properties, adequately accounts for the well-documented antiallergic activity of tissue and urine extracts on isolated smooth muscle preparations and in guinea pigs in vivo. This review summarizes the investigations leading to the discovery of this lipid class. It is postulated that the observed antiallergic activity of 2,4-diketones may be explained by the intracellular sequestration of calcium ions transiently liberated from intracellular storage pools after an agonist-receptor interaction, thus blocking response to the agonist. The true physiological function (or functions) of this lipid class has not been defined. The chelating properties of 2,4-diketones suggest their involvement in intracellular ionic interactions.