LacCer(d18:1/12:0) is a lactosylceramide or LacCer. Lactosylceramides are the most important and abundant of the diosylceramides. Lactosylceramides (LacCer) were originally called 'cytolipin H'. It is found in small amounts only in most animal tissues, but it has a number of significant biological functions and it is of great importance as the biosynthetic precursor of most of the neutral oligoglycosylceramides, sulfatides and gangliosides. In animal tissues, biosynthesis of lactosylceramide involves addition of the second monosaccharides unit (galactose) as its nucleotide derivative to monoglucosylceramide, catalysed by a specific beta-1,4-galactosyltransferase on the lumenal side of the Golgi apparatus. The glucosylceramide precursor must first cross from the cytosolic side of the membrane, possibly via the action of a flippase. The lactosylceramide produced can be further glycosylated or transferred to the plasma membrane. Lactosylceramide may assist in stabilizing the plasma membrane and activating receptor molecules in the special micro-domains or rafts, as with the cerebrosides. It may also have its own specialized function in the immunological system in that it is known to bind to specific bacteria. In addition, it is believed that a number of pro-inflammatory factors activate lactosylceramide synthase to generate lactosylceramide, which in turn activates "oxygen-sensitive" signalling pathways that affect such cellular processes as proliferation, adhesion, migration and angiogenesis. Dysfunctions in these pathways can affect several diseases of the cardiovascular system, cancer and inflammatory states, so lactosylceramide metabolism is a potential target for new therapeutic treatments. beta-D-galactosyl-1,4-beta-D-glucosylceramide is the second to last step in the synthesis of N-Acylsphingosine and is converted. from Glucosylceramide via the enzyme beta-1,4-galactosyltransferase 6 (EC:2.4.1.-). It can be converted to Glucosylceramide via the enzyme beta-galactosidase (EC:3.2.1.23). Moreover, lactosylceramide (D18:1/12:0) is found to be associated with abetalipoproteinemia and hypobetalipoproteinemia, which are inborn errors of metabolism.