Desosamine is a 3-(dimethylamino)-3,4,6-trideoxyhexose found in certain

macrolide antibiotics Macrolides are a class of mostly natural products with a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. Macrolides belong to the polyketide class of natural products. So ...

(contain a high level of microbial resistance) such as the commonly prescribed

erythromycin Erythromycin is an antibiotic used for the treatment of a number of bacterial infections. This includes respiratory tract infections, skin infections, chlamydia infections, pelvic inflammatory disease, and syphilis. It may also be used ...

azithromycin Azithromycin, sold under the brand names Zithromax (in oral form) and Azasite (as an eye drop), is an antibiotic medication used for the treatment of several bacterial infections. This includes otitis media, middle ear infections, strep throa ...

clarithromycin Clarithromycin, sold under the brand name Biaxin among others, is an antibiotic used to treat various bacterial infections. This includes strep throat, pneumonia, skin infections, '' H. pylori'' infection, and Lyme disease, among others. Clari ...

, methymycin, narbomycin,

oleandomycin Oleandomycin is a macrolide antibiotic. It is synthesized from strains of ''Streptomyces antibioticus''. It is weaker than erythromycin. It used to be sold under the brand name Sigmamycine, combined with tetracycline, and made by the company R ...

, picromycin and

roxithromycin Roxithromycin is a semi-synthetic macrolide antibiotic used to treat respiratory tract, urinary and soft tissue infections. It is a derivative of erythromycin - comprising the same 14-membered lactone ring - with an oxime-based side chain attac ...

. As the name suggests, these macrolide antibiotics contain a macrolide or lactone ring and they are attached to the ring desosamine which is crucial for bactericidal activity. The biological action of the desosamine-based macrolide antibiotics is to inhibit the bacterial ribosomal protein synthesis. These antibiotics which contain desosamine are widely used to cure bacterial infections in human respiratory system, skin, muscle tissues, and urethra.

Discovery

Although desosamine has been found in many macrolide antibiotics, the complete chemical structure of desosamine was not determined until 1962.

Nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...

spectroscopy data was used to establish the complete configuration of desosamine. The hydrogen atoms at the C1,C2,C3, and C5 positions are all found to be axial.

Biosynthesis

Six

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s are required for desosamine biosynthesis from

TDP-glucose Thymidine diphosphate glucose (often abbreviated dTDP-glucose or TDP-glucose) is a nucleotide-linked sugar consisting of deoxythymidine diphosphate linked to glucose. It is the starting compound for the syntheses of many deoxysugars. Biosynthes ...

in ''Streptomyces venezuelae''. In addition to the required enzymes, there are eight important open reading frames known as the des regions, they are desI~desVIII, these eight frames are the necessary genes used in desosamine biosynthesis, among the 8 des regions, the desI gene implements C-4 deoxygenation by the enzymatic activity of dehydrase.

Degradation

Degradation of several of the aforementioned antibiotics yields the desosamine sugar. It is found in combination with the smaller macrolide rings, always attached at C-3 or C-5 of the aglycone. Alkaline degradation found the sugar to be a D-hexose derivative. Glycosidic cleavage of methomycin produces aglycone methynolide and the basic sugar desosamine, whose structure had been determined by oxidative degradation to crotonaldehyde and by other experiments.

Drug resistance

Macrolide antibiotics that contain desosamine as an amino sugar in their chemical structures sometimes encounter drug-resistant bacteria. The target-site modification can result in changing chemical structure of the antibiotics, for example, a methylation mutation, which will block the drug from normally functioning.

References

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External links