Phospholipids are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue. Marine phospholipids typically have omega-3 fatty acids EPA and DHA integrated as part of the phospholipid molecule. The phosphate group can be modified with simple organic molecules such as choline, ethanolamine or serine.
Sicariidae is a family of six-eyed venomous spiders known for their potentially necrotic bites. The family consists of three genera and about 160 species. Well known spiders in this family include the brown recluse spider and the six-eyed sand spider.
Sphingomyelin is a type of sphingolipid found in animal cell membranes, especially in the membranous myelin sheath that surrounds some nerve cell axons. It usually consists of phosphocholine and ceramide, or a phosphoethanolamine head group; therefore, sphingomyelins can also be classified as sphingophospholipids. In humans, SPH represents ~85% of all sphingolipids, and typically make up 10–20 mol % of plasma membrane lipids.
Ceramides are a family of waxy lipid molecules. A ceramide is composed of sphingosine and a fatty acid joined by an amide bond. Ceramides are found in high concentrations within the cell membrane of eukaryotic cells, since they are component lipids that make up sphingomyelin, one of the major lipids in the lipid bilayer. Contrary to previous assumptions that ceramides and other sphingolipids found in cell membrane were purely supporting structural elements, ceramide can participate in a variety of cellular signaling: examples include regulating differentiation, proliferation, and programmed cell death (PCD) of cells.
Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes. These enzymes belong to a larger superfamily of Phospholipase C. Other families of phospholipase C enzymes have been identified in bacteria and trypanosomes. Phospholipases C are phosphodiesterases.
Lipid signaling, broadly defined, refers to any biological signaling event involving a lipid messenger that binds a protein target, such as a receptor, kinase or phosphatase, which in turn mediate the effects of these lipids on specific cellular responses. Lipid signaling is thought to be qualitatively different from other classical signaling paradigms because lipids can freely diffuse through membranes. One consequence of this is that lipid messengers cannot be stored in vesicles prior to release and so are often biosynthesized "on demand" at their intended site of action. As such, many lipid signaling molecules cannot circulate freely in solution but, rather, exist bound to special carrier proteins in serum.
Phospholipase D (EC 3.1.4.4, lipophosphodiesterase II, lecithinase D, choline phosphatase, PLD; systematic name phosphatidylcholine phosphatidohydrolase) is an enzyme of the phospholipase superfamily that catalyses the following reaction
3′,5′-cyclic-nucleotide phosphodiesterases (EC 3.1.4.17) are a family of phosphodiesterases. Generally, these enzymes hydrolyze a nucleoside 3′,5′-cyclic phosphate to a nucleoside 5′-phosphate:
Sphingomyelin phosphodiesterase is a hydrolase enzyme that is involved in sphingolipid metabolism reactions. SMase is a member of the DNase I superfamily of enzymes and is responsible for breaking sphingomyelin (SM) down into phosphocholine and ceramide. The activation of SMase has been suggested as a major route for the production of ceramide in response to cellular stresses.
Sicarius is a genus of recluse spiders that is potentially medically significant to humans. It is one of three genera in its family, all venomous spiders known for a bite that can induce loxoscelism. They live in deserts and arid regions of the Neotropics, and females use a mixture of sand and silk when producing egg sacs. The name is Latin for assassin.
The enzyme phosphatidylinositol diacylglycerol-lyase catalyzes the following reaction:
In enzymology, a ceramide cholinephosphotransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a ceramide kinase, also abbreviated as CERK, is an enzyme that catalyzes the chemical reaction:
Sphingomyelin phosphodiesterase 1 (SMPD1), also known as acid sphingomyelinase (ASM), is an enzyme that in humans is encoded by the SMPD1 gene.
Phospholipase C (PLC) is a class of membrane-associated enzymes that cleave phospholipids just before the phosphate group (see figure). It is most commonly taken to be synonymous with the human forms of this enzyme, which play an important role in eukaryotic cell physiology, in particular signal transduction pathways. Phospholipase C's role in signal transduction is its cleavage of phosphatidylinositol 4,5-bisphosphate (PIP2) into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), which serve as second messengers. Activators of each PLC vary, but typically include heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca2+, and phospholipids.
In molecular biology, zinc-dependent phospholipases C is a family of bacterial phospholipases C enzymes, some of which are also known as alpha toxins.
Ectonucleotide pyrophosphatase/phosphodiesterase family member 7 also known as alkaline sphingomyelin phosphodiesterase (Alk-SMase) or intestinal alkaline sphingomyelinase is an enzyme that in humans is encoded by the ENPP7 gene.
Lipase is a family of enzymes that catalyzes the hydrolysis of fats. Some lipases display broad substrate scope including esters of cholesterol, phospholipids, and of lipid-soluble vitamins and sphingomyelinases; however, these are usually treated separately from "conventional" lipases. Unlike esterases, which function in water, lipases "are activated only when adsorbed to an oil–water interface". Lipases perform essential roles in digestion, transport and processing of dietary lipids in most, if not all, organisms.
Functional inhibitors of acid sphingomyelinase, or FIASMA, is a large group of pharmacological compounds inhibiting the enzyme acid sphingomyelinase. This enzyme is mainly located within the lysosome, where it cleaves sphingomyelin to ceramide and sphingosine, the latter of which is then phosphorylated to sphingosine-1-phosphate. These metabolites, and subsequent inhibition of the enzyme, influence the balance between cell death (apoptosis) and cell growth (proliferation). A lack of regulation of this sensitive equilibrium can lead to serious clinical consequences.
Acid sphingomyelinase is one of the enzymes that make up the sphingomyelinase (SMase) family, responsible for catalyzing the breakdown of sphingomyelin to ceramide and phosphorylcholine. They are organized into alkaline, neutral, and acidic SMase depending on the pH in which their enzymatic activity is optimal. Acid Sphingomyelinases (aSMases) enzymatic activity can be influenced by drugs, lipids, cations, pH, redox and other proteins in the environment. Specifically aSMases have been shown to have increased enzymatic activity in lysobisphosphatidic acid (LBPA) or phosphatidylinositol (PI) enriched environments, and inhibited activity when phosphorylated derivatives of PI are present.
