The three major metabolic pathways of ceramide biosynthesis

Major metabolic pathways of ceramide biosynthesis: the de novo pathway (pink background), the salvage pathway (light blue background), and the sphingomyelin hydrolysis pathway (green background). Genes encoding enzymes involved in these pathways are shown in italics. ASAH1, lysosomal ceramidase; ASAH2, plasma membrane ceramidase; ACER2, Golgi ceramidase; ACER3, endoplasmic reticulum and Golgi ceramidase; CERS1, 2, 5, and 6, ceramide synthases; DEGS1, dihydroceramide desaturase; CERK, ceramide kinase; SGMS1, sphingomyelin synthase 1; SMPD1, lysosomal sphingomyelin phosphodiesterase 1; SMPD2, neutral sphingomyelin phosphodiesterase 2; GBA1, glucosylceramidase beta 1; SPT1, serine palmitoyltransferase; KDSR, 3-ketodihydrosphingosine reductase; SPHK, sphingosine kinase; SGPP1, sphingosine-1-phosphate phosphatase 1. (Source: Kyriakou K, Lederer CW, Kleanthous M, Drousiotou A, Malekkou A. Acid Ceramidase Depletion Impairs Neuronal Survival and Induces Morphological Defects in Neurites Associated with Altered Gene Transcription and Sphingolipid Content. Int J Mol Sci 2020;21(5):1607. Creative Commons Attribution license [CC BY] license. http://creativecommons.org/licenses/by/4.0. Image edited considerably from original by Douglas J Lanska MD MS MSPH.)