What is the function of sphingomyelinase?
Introduction: Sphingomyelinases, which catalyze the hydrolysis of sphingomyelin to ceramide and phosphorylcholine, are abundant in the brain. These enzymes are a major, rapid source of ceramide production not only during physiological responses to receptor stimulation, but also in neurological disorders.
How does acid sphingomyelinase work?
The enzyme acid sphingomyelinase catalyzes the hydrolysis of sphingomyelin to ceramide. The importance of the enzyme for cell functions was first recognized in Niemann-Pick disease type A and B, the genetic disorders with a massive accumulation of sphingomyelin in many organs.
What are the products of sphingomyelinase?
Abstract. Sphingomyelinases (SMases) hydrolyse sphingomyelin, releasing ceramide and creating a cascade of bioactive lipids. These lipids include sphingosine and sphingosine-1-phosphate, all of which have a specific signalling capacity.
Is sphingomyelinase a lysosomal enzyme?
A-SMase is a lysosomal/endosomal enzyme that is translocated to the plasma membrane outer leaflet on activation of the death receptor Fas.
What is the substrate for sphingomyelinase?
As indicated by their name, the primary substrate of these enzymes in mammals is SM, which is hydrolysed to yield ceramide and choline-phosphate (ChoP) (Jenkins et al., 2011).
Where are Cerebrosides found?
Cerebrosides are abundant in brain white matter and nerve myelin sheaths and they are present in small quantity within the cell membranes of other tissues. Brain white matter and, to a lesser extent, other tissues, also have lipids that contain sulfur.
What is acid sphingomyelinase deficiency?
Acid sphingomyelinase deficiency (ASMD) is a rare progressive genetic disorder that results from a deficiency of the enzyme acid sphingomyelinase, which is required to break down (metabolize) a fatty substance (lipid) called sphingomyelin.
Which of the following diseases is caused by a deficiency of sphingomyelinase?
Niemann-Pick disease results from a deficiency of sphingomyelinase that causes accumulation of sphingomyelin in the cells of the reticuloendothelial and central nervous systems. As in Gaucher disease, there is an infantile form of Niemann-Pick disease that is rapidly fatal.
What is the difference between cerebrosides and gangliosides?
Cerebrosides are sphingolipids that contain a sugar unit. The sphingolipids called gangliosides are more complex, usually containing a branched chain of three to eight monosaccharides and/or substituted sugars.
What causes ASMD?
What causes ASMD? ASMD is an inherited condition caused by genetic variants (changes in your genes). These changes can alter certain processes in your body and result in disease. The gene involved in ASMD is called SMPD1.
What is sphingomyelinase activation?
Sphingomyelinase activation occurs in different cardiovascular system cell types, namely cardiac myocytes, endothelial and vascular smooth muscle cells, mediating cell proliferation, cell death, and contraction of cardiac and vascular myocytes.
What is Zn2+-stimulated sphingomyelinase?
Zn 2+ -stimulated sphingomyelinase is secreted by many cell types and is a product of the acid sphingomyelinase gene . . Human vascular endothelial cells are a rich and regulatable source of secretory sphingomyelinase.
How are sphingomyelin vesicles formed?
Many cell types express a SMase that can be secreted or delivered to endosomes and lysosomes. The hydrolysis of sphingomyelin by these enzymes is activated by several signaling pathways, and this may lead to formation of vesicles by the process described here.
What is the difference between sphingomyelinase and ceramide?
Sphingomyelinases ensure ceramide production. The term ceramide refers to a family of at least 50 distinct, highly hydrophobic molecules containing a variable length fatty acid (2–28 carbons) linked to sphingosine or a related long-chain base.