noun, plural: octoses
Monosaccharides are the simplest form of carbohydrates. They are classified according to the number of carbon atoms in a monosaccharide. In particular, an octose is a monosaccharide with eight carbon atoms. Monosaccharides may also be classified based on the type of carbonyl group they contain. An aldose is a monosaccharide that contains an aldehyde group (-CHO) at position 1 whereas a ketose is one that contains a ketone (C=O) at position 2. Thus, an aldooctose would be an octose with an aldehyde group. A ketooctose, in contrast, would be an octose with a ketone functional group.
Octoses have a chemical formula of C8H16O8. An example is methylthiolincosamide, i.e. the sugar moiety of the antimicrobial agent lincomycin A. This antibiotic has been used to treat Gram-positive infections. The ostose moiety is linked to an amino acid derivative (i.e. propulhygric acid) via an amide bond. The biosynthesis of lincomycin involves a metabolic pathway comprised of two phases. In the first phase, methylthiolincosamide and propylproline are produced separately. They are condensed to form N-demethylincomycin. This is then methylated through S-adenosylmethionine.
Word origin: oct(o)- ("eight") + -ose (relating to sugars)