Sinefungin, a Natural Nucleoside Analogue of S-Adenosylmethionine, Inhibits Streptococcus pneumoniae Biofilm Growth

Figure 7

Systematic diagram of cyclic production of homocysteine and activated methyl cycle in Streptococcus pneumoniae. Methionine is converted into SAM by SAM synthetase (MetK). Donation of the methyl group of SAM to a variety of methyl acceptors results in SAH; the MTA/SAH nucleosidase (pfs) first converts SAH into S-ribosylhomocysteine (SRH) which is then recycled back to homocysteine by LuxS. As a byproduct of this reaction, 4,5-dihydroxy 2,3-pentanedione is produced which spontaneously forms autoinducer-2. The decarboxylation of SAM produces MTA (methylthioadenosine) as catalyzed by spermidine synthase (speE). Spermidine (a polyamine) is the byproduct of this reaction from putrescine.