''N''-Acetylneuraminic acid (Neu5Ac or NANA) is the predominant

sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this gr ...

found in human cells, and many mammalian cells. Other forms, such as N-Glycolylneuraminic acid, may also occur in cells. This residue is negatively charged at physiological pH and is found in complex

glycans The terms glycans and polysaccharides are defined by IUPAC as synonyms meaning "compounds consisting of a large number of monosaccharides linked glycosidically". However, in practice the term glycan may also be used to refer to the carbohydrate p ...

mucin Mucins () are a family of high molecular weight, heavily glycosylated proteins (glycoconjugates) produced by epithelial tissues in most animals. Mucins' key characteristic is their ability to form gels; therefore they are a key component in most ...

s and glycoproteins found at the

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

. Neu5Ac residues are also found in glycolipids, known as

ganglioside A ganglioside is a molecule composed of a glycosphingolipid (ceramide and oligosaccharide) with one or more sialic acids (e.g. ''N''-acetylneuraminic acid, NANA) linked on the sugar chain. NeuNAc, an acetylated derivative of the carbohydrate sia ...

s, a crucial component of neuronal membranes found in the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

. Along with involvement in preventing infections (

mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...

associated with

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

s—mouth, nose, GI, respiratory tract), Neu5Ac acts as a receptor for

influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...

viruses, allowing attachment to mucous cells via

hemagglutinin In molecular biology, hemagglutinins (or ''haemagglutinin'' in British English) (from the Greek , 'blood' + Latin , 'glue') are receptor-binding membrane fusion glycoproteins produced by viruses in the ''Paramyxoviridae'' family. Hemagglutinins ar ...

(an early step in acquiring influenzavirus infection).

In the biology of bacterial pathogens

Neu5Ac is also important in the biology of a number of pathogenic and symbiotic bacteria as it can used either as a nutrient, providing both carbon and nitrogen to the bacteria, or in some pathogens, can be activated and placed on the cell surface. Bacteria have evolved transporters for Neu5Ac to enable them to capture it from their environment and a number of these have been characterized including the NanT protein from ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...

'', the SiaPQM

TRAP A trap is a mechanical device used to capture or restrain an animal for purposes such as hunting, pest control, or ecological research. Trap or TRAP may also refer to: Art and entertainment Films and television * ''Trap'' (2015 film), Fil ...

transporter from ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria ...

'' and the SatABCD

ABC transporter The ATP-binding cassette transporters (ABC transporters) are a transport system superfamily that is one of the largest and possibly one of the oldest gene families. It is represented in all extant phyla, from prokaryotes to humans. ABC transp ...

from ''

Haemophilus ducreyi ''Haemophilus ducreyi'' is a fastidious gram-negative coccobacillus bacteria. It causes the sexually transmitted disease chancroid, a major cause of genital ulceration in developing countries characterized by painful sores on the genitalia. Ch ...

''.

References

{{DEFAULTSORT:Acetylneuraminic Acid, N- Amino sugars Sugar acids Monosaccharides

In the biology of bacterial pathogens

See also

References