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Schlagwörter:
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Zusammenfassung:
S-adenosyl-l-methionine (SAM) is a necessary cosubstrate for numerous
essential enzymatic reactions including protein and nucleotide
methylations, secondary metabolite synthesis and radical-mediated
processes. Radical SAM enzymes produce 5MODIFIER LETTER
PRIME-deoxyadenosine, and SAM-dependent enzymes for polyamine,
neurotransmitter and quorum sensing compound synthesis produce 5MODIFIER
LETTER PRIME-methylthioadenosine as by-products. Both are inhibitory and
must be addressed by all cells. This work establishes a bifunctional
oxygen-independent salvage pathway for 5MODIFIER LETTER
PRIME-deoxyadenosine and 5MODIFIER LETTER PRIME-methylthioadenosine in
both Rhodospirillum rubrum and Extraintestinal Pathogenic Escherichia
coli. Homologous genes for this pathway are widespread in bacteria,
notably pathogenic strains within several families. A phosphorylase
(Rhodospirillum rubrum) or separate nucleoside and kinase (Escherichia
coli) followed by an isomerase and aldolase sequentially function to
salvage these two wasteful and inhibitory compounds into adenine,
dihydroxyacetone phosphate and acetaldehyde or
(2-methylthio)acetaldehyde during both aerobic and anaerobic growth.
Both SAM by-products are metabolized with equal affinity during aerobic
and anaerobic growth conditions, suggesting that the dual-purpose
salvage pathway plays a central role in numerous environments, notably
the human body during infection. Our newly discovered bifunctional
oxygen-independent pathway, widespread in bacteria, salvages at least
two by-products of SAM-dependent enzymes for carbon and sulfur salvage,
contributing to cell growth.
