Metabolism gets lucky

Mol Syst Biol. 6: 439Not all enzymes are one‐reaction wonders. Indeed, secondary capabilities of enzymes can make metabolism a lot more adaptable than previously thought.Enzymes are usually thought of as specific catalysts of biochemical reactions. Enzyme A acts on substrate B to produce product C. It is, however, becoming increasingly clear that some enzymes are ‘promiscuous’, able to act on alternative substrates to catalyze secondary reactions. A recent study by Kim et al (2010) demonstrates that promiscuity of individual enzymes might be just the tip of the iceberg.Metabolism is a complex network of chemical reactions through which ‘food’ is converted into the many compounds necessary for life. Removal of the enzyme catalyzing a given reaction will break the corresponding metabolic link. Sometimes this will be of no consequence—a similar enzyme might catalyze the same reaction or an alternative route to a downstream product may be present among the established reactions. Kim et al (2010) demonstrate a third possibility. New pathways can be constructed by patching together secondary capabilities of enzymes.Kim et al (2010) start with a bacterium, Escherichia coli , that can produce all of the compounds necessary for growth in a ‘minimal’ medium consisting of …