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Prosaposin
Prosaposin, also known as PSAP, is a protein which in humans is encoded by the ''PSAP'' gene. This highly conserved glycoprotein is a precursor for 4 cleavage products: saposins A, B, C, and D. Saposin is an acronym for Sphingolipid Activator PrO ''SeINs. Each domain of the precursor protein is approximately 80 amino acid residues long with nearly identical placement of cysteine residues and glycosylation sites. Saposins A-D localize primarily to the lysosomal compartment where they facilitate the catabolism of glycosphingolipids with short oligosaccharide groups. The precursor protein exists both as a secretory protein and as an integral membrane protein and has neurotrophic activities. Saposins A–D are required for the hydrolysis of certain sphingolipids by specific lysosomal hydrolases. Family members * Saposin A was identified as an N-terminal domain in the prosaposin cDNA prior to its isolation. It is known to stimulate the enzymatic hydrolysis of 4-methylumbelliferyl-β ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saposin Protein Domain
The saposin domains refers to two evolutionally-conserved protein domains found in saposin and related proteins (SAPLIP). Saposins are small lysosomal proteins that serve as activators of various lysosomal lipid-degrading enzymes. They probably act by isolating the lipid substrate from the membrane surroundings, thus making it more accessible to the soluble degradative enzymes. All mammalian saposins are synthesized as a single precursor molecule (prosaposin) which contains four ''Saposin-B domains'', yielding the active saposins after proteolytic cleavage, and two ''Saposin-A domains'' that are removed in the activation reaction. The Saposin-B domains also occur in other proteins, most of them playing a role in interacting with membranes. Classification The saposin (SapB1-SapB2) domains are found in a wide range of proteins. Each half-domain encodes two alpha helices in the SapB domain for a total of four. The mamallian prosaposin (domain organization below) is a prototypic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfatide
Sulfatide, also known as 3-O-sulfogalactosylceramide, SM4, or sulfated galactocerebroside, is a class of sulfolipids, specifically a class of sulfoglycolipids, which are glycolipids that contain a sulfate group. Sulfatide is synthesized primarily starting in the endoplasmic reticulum and ending in the Golgi apparatus where ceramide is converted to galactocerebroside and later sulfated to make sulfatide. Of all of the galactolipids that are found in the myelin sheath, one fifth of them are sulfatide. Sulfatide is primarily found on the extracellular leaflet of the myelin plasma membrane produced by the oligodendrocytes in the central nervous system and in the Schwann cells in the peripheral nervous system. However, sulfatide is also present on the extracellular leaflet of the plasma membrane of many cells in eukaryotic organisms. Since sulfatide is a multifunctional molecule, it can be used in multiple biological areas. Aside from being a membrane component, sulfatide functions in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metachromatic Leukodystrophy
Metachromatic leukodystrophy (MLD) is a lysosomal storage disease which is commonly listed in the family of leukodystrophies as well as among the sphingolipidoses as it affects the metabolism of sphingolipids. Leukodystrophies affect the growth and/or development of myelin, the fatty covering which acts as an insulator around nerve fibers throughout the central and peripheral nervous systems. MLD involves cerebroside sulfate accumulation. Metachromatic leukodystrophy, like most enzyme deficiencies, has an autosomal recessive inheritance pattern. Signs and symptoms Like many other genetic disorders that affect lipid metabolism, there are several forms of MLD, which are late infantile, juvenile, and adult. * In the ''late infantile form'', which is the most common form of MLD (50–60%), affected children begin having difficulty walking after the first year of life, usually at 15–24 months. Symptoms include muscle wasting and weakness, muscle rigidity, developmental delays, pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tay–Sachs Disease
Tay–Sachs disease is a genetic disorder that results in the destruction of nerve cells in the brain and spinal cord. The most common form is infantile Tay–Sachs disease, which becomes apparent around three to six months of age, with the baby losing the ability to turn over, sit, or crawl. This is then followed by seizures, hearing loss, and inability to move, with death usually occurring by the age of three to five. Less commonly, the disease may occur in later childhood or adulthood (juvenile or late-onset). These forms tend to be less severe, but the juvenile form typically results in death by age 15. Tay–Sachs disease is caused by a genetic mutation in the ''HEXA'' gene on chromosome 15, which codes form a subunit of the hexosaminidase enzyme known as hexosaminidase A. It is inherited from a person's parents in an autosomal recessive manner. The mutation disrupts the activity of the enzyme, which results in the build-up of the molecule GM2 ganglioside within cells, lea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gaucher Disease
Gaucher's disease or Gaucher disease () (GD) is a genetic disorder in which glucocerebroside (a sphingolipid, also known as glucosylceramide) accumulates in cells and certain organs. The disorder is characterized by bruising, fatigue, anemia, low blood platelet count and enlargement of the liver and spleen, and is caused by a hereditary deficiency of the enzyme glucocerebrosidase (also known as glucosylceramidase), which acts on glucocerebroside. When the enzyme is defective, glucocerebroside accumulates, particularly in white blood cells and especially in macrophages (mononuclear leukocytes, which is often a target for intracellular parasites). Glucocerebroside can collect in the spleen, liver, kidneys, lungs, brain, and bone marrow. Manifestations may include enlarged spleen and liver, liver malfunction, skeletal disorders or bone lesions that may be painful, severe neurological complications, swelling of lymph nodes and (occasionally) adjacent joints, distended abdomen, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Degradative Enzyme
A degradative enzyme is an enzyme (in a broader sense a protein) which degrades biological molecules. Some examples of degradative enzymes: *Lipase, which digests lipids, *Carbohydrases, which digest carbohydrates (e.g., sugars), *Proteases, which digest proteins,Hedstrom L. ''Serine Protease Mechanism and Specificity.'' Chem Rev 2002;102:4501-4523. *Nucleases, which digest nucleic acids. *Cathelicidins, antimicrobial polypeptides found in lysosomes. References See also * Hydrolase Hydrolase is a class of enzyme 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 este ... Enzymes {{Enzyme-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GM2A
GM2 ganglioside activator also known as GM2A is a protein which in humans is encoded by the ''GM2A'' gene. Function The protein encoded by this gene is a small glycolipid transport protein which acts as a substrate specific co-factor for the lysosomal enzyme β-hexosaminidase A. β-hexosaminidase A, together with GM2 ganglioside activator, catalyzes the degradation of the ganglioside GM2, and other molecules containing terminal N-acetyl hexosamines. GM2A is a lipid transfer protein that stimulates the enzymatic processing of gangliosides, and also T-cell activation through lipid presentation. This protein binds molecules of ganglioside GM2, extracts them from membranes, and presents them to beta-hexosaminidase A for cleavage of N-acetyl-D-galactosamine and conversion to GM3. It was identified as a member of ML domain family of proteins involved in innate immunity and lipid metabolism in the SMART database. Regulation In melanocytic cells GM2A gene expression may be regu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arylsulfatase A
Arylsulfatase A (or cerebroside-sulfatase) is an enzyme that breaks down sulfatides, namely cerebroside 3-sulfate into cerebroside and sulfate. In humans, arylsulfatase A is encoded by the ''ARSA'' gene. Pathology A deficiency is associated with metachromatic leukodystrophy, an autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ... disease. Biochemistry Enzyme regulation Arylsulfatase A is inhibited by phosphate, which forms a covalent bond with the active site 3-oxoalanine. ; References Further reading * * * * * * * * * * * * * * * * * * External links GeneReviews/NCBI/NIH/UW entry on Arylsulfatase A Deficiency - Metachromatic Leukodystrophy OMIM entries on ARSA Deficiency * * * {{hydrolase-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and noncoding genes. During gene expression, the DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glucocerebroside
Glucocerebroside (also called glucosylceramide) is any of the cerebrosides in which the monosaccharide head group is glucose. Clinical significance In Gaucher disease, the enzyme glucocerebrosidase is nonfunctional and cannot break down glucocerebroside into glucose and ceramide in the lysosome. Affected macrophages, called Gaucher cells, have a distinct appearance similar to "wrinkled tissue paper" under light microscopy, because the substrates build-up within the lysosome. See also * Glucosylceramide synthase * Gauchers disease * Glucocerebrosidase β-Glucocerebrosidase (also called acid β-glucosidase, D-glucosyl-N-acylsphingosine glucohydrolase, or GCase) is an enzyme with glucosylceramidase activity () that is needed to cleave, by hydrolysis, the beta-glycosidic linkage of the chemical g ... References External links * * Glycolipids Carbohydrates {{biochem-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurotrophin
Neurotrophins are a family of proteins that induce the survival, development, and function of neurons. They belong to a class of growth factors, secreted proteins that can signal particular cells to survive, differentiate, or grow. Growth factors such as neurotrophins that promote the survival of neurons are known as neurotrophic factors. Neurotrophic factors are secreted by target tissue and act by preventing the associated neuron from initiating programmed cell death – allowing the neurons to survive. Neurotrophins also induce differentiation of progenitor cells, to ''form'' neurons. Although the vast majority of neurons in the mammalian brain are formed prenatally, parts of the adult brain (for example, the hippocampus) retain the ability to grow new neurons from neural stem cells, a process known as neurogenesis. Neurotrophins are chemicals that help to stimulate and control neurogenesis. Terminology According to the United States National Library of Medicine's medical sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
