The synthetic pathways of ceramide are two pathway. First is the way SMase produces ceramide from SM. Second is de nove pathway by SMS. Acidic SMnase KO mice have a resistance for apoptosis. Acidic SMase is localized in lysosome. Abnormal acumulation of SM induced by delation of acidic SMase leads to Niemanpick A and B disease. Which SM is gonna be cut by acidic SMase? As you know, acidic SMase is localized in lysosome. However, vesicle is released in some condition. So there is a possiblity that SMase is release to out of cell and cut the SM on the plasma membrane. [[SMase01>http://www.j-tokkyo.com/2001/C12N/JP2001-037492.shtml]] [[SMase02>http://wwwsoc.nii.ac.jp/jbiochem/magazine/79-12-06.pdf]]
