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|Section2= |Section3= }} ''N''-Acetylmannosamine is a hexosamine monosaccharide. It is a neutral, stable naturally occurring compound. N-Acetylmannosamine is also known as N-Acetyl-D-mannosamine monohydrate, (which has the CAS Registry Number: 676347-48-1), N-Acetyl-D-mannosamine which can be abbreviated to ManNAc or, less commonly, NAM). ManNAc is the first committed biological precursor of N-acetylneuraminic acid (Neu5Ac, sialic acid) (Figure 1). Sialic acids are the negatively charged, terminal monosaccharides of carbohydrate chains that are attached to glycoproteins and glycolipids (glycans). == Biological role of ManNAc == ManNAc is the first committed biological precursor of Neu5Ac. The initiation of sialic acid biosynthesis occurs in the cytoplasm. The main substrate for this pathway is UDP-GlcNAc, which is derived from glucose. In the rate-limiting step of the pathway, UDP-GlcNAc is converted into ManNAc by UDP-GlcNAc 2-epimerase, encoded by the epimerase domain of GNE. ManNAc is phosphorylated by ManNAc kinase encoded by the kinase domain of GNE. Sialic acid becomes “activated” by CMP-sialic acid synthetase in the nucleus. CMP-sialic acid acts as a sialic acid donor to sialylate glycans on nascent glycoproteins and glycolipids in the Golgi apparatus; it also acts as a cytoplasmic feedback inhibitor of the UDP-GlcNAc 2-epimerase enzyme by binding to its allosteric site. The UDP-GlcNAc 2-epimerase kinase is the rate limiting step in sialic acid biosynthesis. If the enzyme does not work efficiently the organism cannot function correctly. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「N-Acetylmannosamine」の詳細全文を読む スポンサード リンク
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