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|Section2= |Section3= }} ''N''-Glycolylneuraminic acid (Neu5Gc) is a sialic acid molecule found in most mammals. Humans cannot synthesize Neu5Gc because the human gene CMAH is irreversibly mutated, though it is found in apes. It is absent in human tissues because of inactivation of gene encoding CMP-N-acetylneuraminic acid hydroxylase. The gene CMAH encodes for CMP-N-acetylneuraminic acid hydroxylase, which is the enzyme responsible for CMP-Neu5Gc from CMP-N-acetylneuraminic (CMP-Neu5Ac) acid. This loss of the CMAH was estimated to have occurred two to three millions of years ago, which occurred just before the emergence of the genus ''Homo''.〔 Neu5Gc is closely related to the commonly known ''N''-acetylneuraminic acid (Neu5Ac). Neu5Ac differs by a single oxygen atom that is added in the cytosol of a cell. In many mammals, both of these molecules are transferred into the Golgi so that they may be added to many glycoconjugates. However, in humans, Neu5Gc is not present. ==Elimination of Neu5Gc gene in the humans== With the loss of Neu5Gc gene and gain of excess Neu5Ac, it should have affected the interactions of pathogens and humans. Humans should have been less susceptible to Neu5Gc-binding pathogens and more susceptible to Neu5Ac-binding pathogens. It is suggested that human ancestors survived a then-prevailing malaria by eliminating their Neu5Gc production. However, with the rise of ''Plasmodium falciparum'', the parasite that causes malaria today, humans were once again endangered as this new strain of the malaria had a binding preference to the Neu5Ac-rich erythrocytes in humans.〔 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-Glycolylneuraminic acid」の詳細全文を読む スポンサード リンク
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