Enzyme catalysis, the power of certain proteins to accelerate chemical reactions in the cell with extraordinary speed and fascinating precision, remains one of the great mysteries of living systems to this day. The reactions in question range from the simple hydrolysis of peptide bonds to highly complex poly-electronic processes, such as the reduction of oxygen to water catalyzed by cytochrome oxidase, a key enzyme in respiration, or the oxidation of water to oxygen by the photosynthetic apparatus of plants. We're also talking about long-distance electron transfer reactions (several tens of angstroms), which play decisive roles in many cellular processes.
What is the origin of this phenomenon? There's no simple answer to this question, and over the last 50 years it has fuelled a great deal of research and controversy. The chemist's reductionist approach, based on biomimetic and bio-inspired systems, is an original contribution to this quest. However, it seems that one of the keys to this mystery lies in the repeated use, by living organisms, of metal ions conferring unique properties on proteins. Life is therefore not only organic but also "mineral", and biological chemistry not only bio-organic but also bio-inorganic. These metals played a decisive role some 3.5 billion years ago in the emergence of life and, a little later, in the appearance and use of molecular oxygen.
The aim of this lecture was to introduce a number of concepts concerning enzyme catalysis, the chemical properties of metal ions and the activation of small molecules, in this case oxygen and water, by complex natural multi-electronic systems.