Remote Enzyme Microsurgery

摘要

Enzymes achieve astounding rate enhancements of even difficult reactions. They often covalently modify their substrates by their own functional groups, a tactic that enables them to access mechanistic pathways that would not be feasible in solution. The standard amino acid building blocks of enzymes are replete with nucleophiles to use in this "covalent catalysis," but they are essentially devoid of useful electrophiles. An enzyme can bind an exogenous cofactor such as pyridoxal 5'-phos-phate in its active site to correct this deficiency. An elegant alternative is the in situ construction of an electrophile, subsequent to protein synthesis, from amino acids in the active site (1). On page 1392 of this issue, Jensen et al. reveal how a particularly intricate example of this enzyme microsurgery is accomplished (see the figure) (2).