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Sialate O-acetylesterase
The enzyme sialate O-acetylesterase (EC 3.1.1.53) catalyzes the reaction :''N''-acetyl-''O''-acetylneuraminate + H2O = ''N''-acetylneuraminate + acetate In human it is encoded by the SIAE gene located on chromosome 11. This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. The systematic name of this enzyme class is ''N''-acyl-''O''-acetylneuraminate ''O''-acetylhydrolase. Other names in common use include ''N''-acetylneuraminate acetyltransferase, sialate 9(4)-''O''-acetylesterase, and sialidase. Function SIAE activity negatively regulates B lymphocyte antigen receptor signalling and is required for the maintenance of immunological tolerance. It down-regulates B lymphocyte antigen receptor signaling (involving CD22), and is required for immunological tolerance e.g. in mice. Structure The SIAE gene contains 15 exons and expresses a protein that is approximately 56 kDa in size. It is known to be expressed in the adult testis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalysis
Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. The rate increase occurs because the catalyst allows the reaction to occur by an alternative mechanism which may be much faster than the noncatalyzed mechanism. However the noncatalyzed mechanism does remain possible, so that the total rate (catalyzed plus noncatalyzed) can only increase in the presence of the catalyst and never decrease. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymorphism (biology)
In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative '' phenotypes'', in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (one with random mating). Ford E.B. 1965. ''Genetic polymorphism''. Faber & Faber, London. Put simply, polymorphism is when there are two or more possibilities of a trait on a gene. For example, there is more than one possible trait in terms of a jaguar's skin colouring; they can be light morph or dark morph. Due to having more than one possible variation for this gene, it is termed 'polymorphism'. However, if the jaguar has only one possible trait for that gene, it would be termed "monomorphic". For example, if there was only one possible skin colour that a jaguar could have, it would be termed monomorphic. The term polyphenism can be used to clarify that the different forms arise from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
