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Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins, monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing energy, signaling, and acting as structural components of cell membranes. Lipids have applications in the cosmetic and food industries, and in nanotechnology.
Hydrolase is a class of enzymes that commonly perform as biochemical catalysts that use water to break a chemical bond, which typically results in dividing a larger molecule into smaller molecules. Some common examples of hydrolase enzymes are esterases including lipases, phosphatases, glycosidases, peptidases, and nucleosidases.
Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connections that allow cells to connect to one another to form tissues. Glycolipids are found on the surface of all eukaryotic cell membranes, where they extend from the phospholipid bilayer into the extracellular environment.
Sphingolipids are a class of lipids containing a backbone of sphingoid bases, which are a set of aliphatic amino alcohols that includes sphingosine. They were discovered in brain extracts in the 1870s and were named after the mythological sphinx because of their enigmatic nature. These compounds play important roles in signal transduction and cell recognition. Sphingolipidoses, or disorders of sphingolipid metabolism, have particular impact on neural tissue. A sphingolipid with a terminal hydroxyl group is a ceramide. Other common groups bonded to the terminal oxygen atom include phosphocholine, yielding a sphingomyelin, and various sugar monomers or dimers, yielding cerebrosides and globosides, respectively. Cerebrosides and globosides are collectively known as glycosphingolipids.
Glycosphingolipids are a subtype of glycolipids containing the amino alcohol sphingosine. They may be considered as sphingolipids with an attached carbohydrate. Glycosphingolipids are a group of lipids and are a part of the cell membrane. They consist of a hydrophobic ceramide part and a glycosidically bound carbohydrate part. This oligosaccharide content remains on the outside of the cell membrane where it is important for biological processes such as cell adhesion or cell–cell interactions. Glycosphingolipids play also important role in oncogenesis and ontogenesis.
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.
Cerebrosides is the common name for a group of glycosphingolipids called monoglycosylceramides which are important components in animal muscle and nerve cell membranes.
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.
Ceramidase is an enzyme which cleaves fatty acids from ceramide, producing sphingosine (SPH) which in turn is phosphorylated by a sphingosine kinase to form sphingosine-1-phosphate (S1P).
The enzyme branched-chain-2-oxoacid decarboxylase (EC 4.1.1.72) catalyzes the chemical reaction
In enzymology, a 3-hydroxypalmitoyl-[acyl-carrier-protein] dehydratase (EC 4.2.1.61) is an enzyme that catalyzes the chemical reaction
The enzyme long-chain-enoyl-CoA hydratase (EC 4.2.1.74) catalyzes the chemical reaction
The enzyme oleate hydratase (EC 4.2.1.53) catalyzes the chemical reaction
Palmitoyl-CoA hydrolase (EC 3.1.2.2) is an enzyme in the family of hydrolases that specifically acts on thioester bonds. It catalyzes the hydrolysis of long chain fatty acyl thioesters of acyl carrier protein or coenzyme A to form free fatty acid and the corresponding thiol:
The enzyme endoglycosylceramidase (EC 3.2.1.123) catalyzes the following chemical reaction:
In enzymology, a long-chain-fatty-acyl-glutamate deacylase (EC 3.5.1.55) is an enzyme that catalyzes the chemical reaction
In enzymology, an aculeacin-A deacylase is an enzyme that catalyzes the chemical reaction that cleaves the amide bond in aculeacin A and related neutral lipopeptide antibiotics, releasing the long-chain fatty acid side chain.
In enzymology, sphingosine N-acyltransferases (ceramide synthases (CerS), EC 2.3.1.24) are enzymes that catalyze the chemical reaction of synthesis of ceramide:
Sphingomyelin deacylase (EC 3.5.1.109, SM deacylase, GcSM deacylase, glucosylceramide sphingomyelin deacylase, sphingomyelin glucosylceramide deacylase, SM glucosylceramide GCer deacylase, SM-GCer deacylase, SMGCer deacylase) is an enzyme with systematic name N-acyl-sphingosylphosphorylcholine amidohydrolase. This enzyme catalyses the following chemical reaction
Ceramide synthase 3 (CersS3), also known as longevity assurance homologue 3, is an enzyme that is encoded in humans by the CERS3 gene.
References
- Hirabayashi Y, Kimura M, Matsumoto M, Yamamoto K, Kadowaki S, Tochikura T (January 1988). "A novel glycosphingolipid hydrolyzing enzyme, glycosphingolipid ceramide deacylase, which cleaves the linkage between the fatty acid and sphingosine base in glycosphingolipids". Journal of Biochemistry. 103 (1): 1–4. PMID 3360750.
