Some of carnitine's most important roles are transporting fatty acids into the mitochondria to be used in fatty acid metabolism and removing cellular waste from the mitochondria. It does this by forming an ester bond with the molecule it is going to transport:

For each unique molecule that carnitine bonds with, it forms a unique acylcarnitine species. The acylcarnitine is then named based on the molecule carnitine has bonded with. In the example above, carnitine bonded with a propionyl group, and was thus named propionylcarnitine. Other examples of acylcarnitine include palmitoylcarnitine, from palmitic acid, linoleoylcarnitine, from linoleic acid and arachidonoylcarnitine, from arachidonic acid. As there are well over 50 fatty acids, there are at least 50 possible acylcarnitine species, plus additional acylcarnitines that are formed when carnitine bonds with something other than a fatty acid. The study of all the acylcarnitine species has been termed the Carnitinome.

Abnormal levels of specific acylcarnitines are associated with certain inborn errors of metabolism or metabolic disorders. Acylcarnitine profiles are frequently used to screen for inborn errors of metabolism, and are most often used in newborns (Rashed 1995). They have been shown to be both sensitive and cost effective (Wiley 1999). While the acylcarnitine profiles are a valuable tool, there are still many questions remaining to be answered concerning acylcarnitines. For instance, is the level of one acylcarnitine affect those of another? Can acylcarnitines be used for more than detection of metabolic disorders? Is supplementing a patient with propionylcarnitine more beneficial than supplementing with free carnitine?

The Carnitinome Database is a database in Microsoft Access that houses available information on each acylcarnitine species. These data include structure of acylcarnitines, available stable isotopes of each species and fragmentation patterns. There is also study information from an ongoing literature search including: sample size of study, sample condition (normal, diabetic, etc), sample type (urine, plasma, etc), method of determining acylcarnitines, and the level of each acylcarnitine in the sample. Queries can be written of the database to pull up desired information. We hope to have the database online by Spring 2007, so that it may used as a tool for researchers around the world.