| 释义 |
Neuraminic Acid
neuraminic acid[¦nu̇r·ə¦min·ik ′as·əd] (biochemistry) C9H17NO8 An amino acid, the aldol condensation product of pyruvic acid and N-acetyl-D-mannosamine, regarded as the parent acid of a family of widely distributed acyl derivatives known as sialic acids. Neuraminic Acid 5-amino-3, 5-deoxy-D-glycero-n-galac-to-2-nonulosonic acid, a natural compound occurring as N- and O-acyl derivatives (sialic acids) in all the organs and tissues of animals and in certain microorganisms. The acyl derivatives of neuraminic acid (the most common of which are N-acetyl and N-glycolyl neuraminic acids) are constituents of natural glycolipids and glycoproteins, where they are bonded to monosaccharide radicals. The neuraminic acid radical is split off from the glycolipid and glycoprotein molecules under the action of the specific enzyme neuraminidase or dilute acids, thereby substantially altering the physicochemical and biological properties of the molecules. Certain pathological conditions (cancer, tuberculosis, mental disorders) induce a marked increase in the neuraminic acid content of fluids and tissues in the human body. In glycolipid form, neuraminic acid takes part in the fixation of certain viruses and neurotoxins in animal organisms. The biosynthesis of neuraminic acid is effected in the presence of hexosa-mine derivatives and pyruvic acid. neuraminic acid
sialidase [si-al´ĭ-dās] 1. an enzyme of the hydrolase class that catalyzes the cleavage of glucosidic linkages between a sialic acid" >sialic acid residue and a hexose" >hexose or hexosamine" >hexosamine residue at the nonreducing terminal of oligosaccharides in glycoproteins, glycolipids, and proteoglycans. Deficiency of it is an autosomal recessive trait and is seen in sialidosis" >sialidosis and galactosialidosis" >galactosialidosis.2. the enzyme with this activity specifically cleaving sialic acid–containing gangliosides; it is deficient in mucolipidosis IV" >mucolipidosis IV. Called also neuraminidase.neur·a·min·ic ac·id (nūr'ă-min'ik as'id), An aldol product of d-mannosamine and pyruvic acid, linking the C-1 of the former to the C-3 of the latter. The N- and O-acyl derivatives of neuraminic acid are known as sialic acids and are constituents of gangliosides and of the polysaccharide components of mucoproteins and glycoproteins from many tissues, secretions, and species. Synonym(s): prehemataminic acidneu·ra·min·ic ac·id (nūr'ă-min'ik as'id) An aldol product of d-mannosamine and pyruvic acid. The N- and O-acyl derivatives of neuraminic acid are known as sialic acids and are constituents of gangliosides and of the polysaccharide components of muco- and glycoproteins from many tissues and secretions. |