The ubiX decarboxylase is not required for the ubiG O-methyltransferase activity
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An essential component of the respiratory chain of aerobic prokaryotes and eukaryotes is Conezyme Q (Ubiquinone, Q), which acts as an electron carrier thereby serving as a link between dehydrogenases and the subsequent electron acceptors in the respiratory chain. In Escherichia coli, during Q biosynthesis, the decarboxylation step is catalyzed by two isofuncational enzymes, UbiD and UbiX. UbiD carries out the decarboxylation of 80% of the substrate, 3-octaprenyl-4-hydroxybenzoate whereas UbiX is responsible for the remaining 20%. It has been reported that the loss of UbiX decreases UbiG O- methyltransferase activity by .36 fold and the growth in Luria-Bertani (LB) broth as well as in succinate minimal medium is severely affected. Contrary to this report, we discovered that the deltaUbiX mutant grows to wild-type levels in both media and synthesizes close to wild-type levels of Q.