InsPCers have been characterized in many plants, fungi, and protozoans but not in animals. There are no well-documented reports of the absence of InsPCers in organisms of these categories and one might possibly consider these lipids to be ubiquitous in plants, fungi, and protozoans. The polar headgroups of these lipids display quite heterogeneous structures depending on the source, including attachment to proteins as possible membrane anchors. The ceramides are with some exceptions composed of phytosphingosine and a very long-chain, usually hydroxylated, fatty acid. The vital nature of such sphingolipids in the plasma membrane is indicated in S. cerevisiae. Clearly, much remains to be discovered about the structure, metabolism, and function of the InsPCers.
