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Biosynthetic pahway
First isolated from the Streptomyces fradiae and Streptomyces albogriseus in 1949 (NBRC 12773). Neomycin is a mixture of neomycin B (framycetin);  and its epimer neomycin  C, the latter component accounting for some 5–15% of the mixture. Neomycin has good activity against Gram-positive and Gram-negative bacteria, but is very ototoxic. Its use is thus restricted to oral treatment of intestinal infections.

Neomycin B is composed of four parts: D-neosamine, 2-deoxystreptamine (2-DOS), D-ribose, and L-neosamine. Neomycin A, also called neamine, contains D-neosamine and 2-deoxystreptamine. Neamine is made from six genes, DOIS gene (btrC, neo7); L-glutamine:DOI aminotransferase gene (btrS, neo6); a putative glycosyltransferase gene (btrM, neo8); a putative aminotransferase (similar to glutamate-1-semialdehyde 2,1- aminomutase) gene (btrB, neo18); a putative alcohol dehydrogenase gene (btrE, neo5); another putative dehydrogenase (similar to chorine dehydrogenase and related flavoproteins) gene (btrQ, neo11). A deacetylase acting to remove the acetyl group on N-acetylglucosamine moieties of aminoglycoside intermediates (Neo16), still needs to be clarified (sequence similar to BtrD).

Next is the attachment of the D-ribose via ribosylation of neamine, using 5-phosphoribosyl-1-diphosphate (PRPP) as the ribosyl donor (BtrL, BtrP); glycosyltransferase (potential homologues RibF, LivF, Parf) gene (Neo15).

Neosamine B (L-neosamine B) is most likely biosynthesized in the same manner as the neosamine C (D-niosamine) in neamine biosynthesis, but with an additional epimerization step required to account for the presence of the epimeric neosamine B in neomycin B.