Global enzymes: Sphere of influence

Abstract

The realization that enzyme-driven molecular discrimination can be detected at the global level induces a sense of vertigo at the immensity of the scale shifts involved. Some enzymes are so central in nature that their discrimination signals are indicators of global changes. Yet, remarkably, these global-scale signals can be recreated with a few cells in a sealed test tube, or with a leaf in a bell jar. Each element has different isotopes, most of which are stable and can be distinguished by their mass. Enzymes catalyse chemical reactions that are sensitive to differences in the dissociation energies of molecules. It is usually easier to form, or break, bonds of molecules that contain the lighter isotope of a given element, because the vibrational frequency of such bonds tends to be higher. Consequently, molecules containing lighter isotopes are preferentially incorporated into the products of incomplete reactions, whereas heavier isotopes become enriched in unreacted residues. These simple, mass-dependent traits give rise to useful signals — stable isotopes can be thought of as natural labels on all environmental processes, allowing us to see a dynamic universe that is normally hidden from view.