Substrate preference of 5′-methylthioadenosine/S-adenosylhomocysteine nucleosidase inBurkholderia thailandensis

Abstract

5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) plays crucial roles in the production of autoinducers and methionine metabolism. Putative genes encoding MTAN and AdoHcyase from Burkholderia thailandensis were cloned and characterized. The K(m) values of MTAN for 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH) were 19 and 58 μM, respectively. The catalytic efficiency of MTAN for SAH was only 0.004% of the value for MTA, indicating an almost complete substrate preference of MTAN for MTA. The results of autoinducer-2 assay of B. thailandensis and recombinants indicated that LuxS enzyme activity was lacking in Burkholderia species. Instead, AdoHcyase hydrolysed SAH directly to homocysteine and adenosine in the activated methyl cycle. Meanwhile, the K(m) value of AdoHcyase for SAH was determined to be 40 μM. Sequence analysis revealed that MTAN had much higher diversity than AdoHcyase, which likely contributes to its substrate preference for MTA. Furthermore, the phylogenetic tree of MTAN sequences revealed that LuxS(+) bacteria could be discriminated from LuxS(-) bacteria. These results suggested that the substrate preference of MTAN for MTA and SAH degradation pathway evolved with the bacterial-activated methyl cycle.

Novel small molecule modulators of quorum sensing in avian pathogenic Escherichia coli (APEC)

“…Adherence and invasion are important for APEC pathogenesis and mediate colonization, survival and spread in the host [33]. Our results suggest that the selected AI-2 inhibitors, with the exception of C4, might interfere with synthesis, secretion, and/ or transport of AI-2 via their effect on the luxS; affecting QS and cognate pathogenicity of APEC [34]. However, C4 also inhibited AI-2 production, this suggests that C4 might intervene at various points in the AI-2 production cycle without having a direct effect on luxS and/ or luxS dependent mechanisms.…”