noun, plural: mannosamines
A hexosamine, wherein mannose contains an amine (-NH2) instead of a hydroxyl (–OH) group
An amino sugar is a sugar molecule wherein the hydroxyl group is replaced by an amine group. Hexosamines are amino sugars wherein the sugar derivative is a hexose. Examples of hexosamines are glucosamine (based upon glucose), galactosamine (based upon galactose), fructosamine (based upon fructose), and mannosamine (based upon mannose).
Mannosamine is an amino sugar derived from mannose. It has a chemical formula of C6H13NO5.
In biological systems, D-mannosamine (2-amino-2-deoxymannose) is a constituent of neuraminic acid. Neuraminic acid is a nonose, i.e. a 9-carbon monosaccharide. All the N- or O-substituted derivatives of neuraminic acid (e.g. N-acetylnuraminic acid) are collectively called sialic acid. Sialic acids occur widely in animal tissues, mostly in glycoproteins and gangliosides. In humans, sialic acid is greatest in amount in the brain where it is involved in neural transmission.
In bacterial systems, sialic acid derivatives are biosynthesized through a chemoenzymatic process using aldolase enzyme. This enzyme catalyzes the insertion of pyruvic acid (three-carbon molecule) to a mannose derivative, such as D-mannosamine (a hexose), thus, producing neuraminic acid.