It is not often realized that the absolute protein specificity is an exception rather than a rule. Two major kinds of protein multi-specificities are promiscuity and moonlighting. This review discusses the idea of enzyme specificity and then focusses on moonlighting. Some important examples of protein moonlighting, such as crystallins, ceruloplasmin, metallothioniens, macrophage migration inhibitory factor, and enzymes of carbohydrate metabolism are discussed. How protein plasticity and intrinsic disorder enable the removing the distinction between enzymes and other biologically active proteins are outlined. Finally, information on important roles of moonlighting in human diseases is updated.
Keywords: Cancer; Ceruloplasmin; Crystallins; Glycolytic enzymes; Intrinsically disordered proteins; Metabolic reprogramming; Metamorphic proteins; Multitasking proteins; Neomorphic moonlighting proteins; Protein plasticity.
© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.