Introductory remarks to the second session

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The four presentations in this session cover studies on different aspects of enzyme structure and function. They effectively illustrate how one has to combine different approaches to arrive at an understanding of enzymatic catalysis and control. Nowadays, the molecular description of an enzyme is hardly credible without detailed crystallographic information. Thus, Dr Blake’s paper on the structure of phosphoglycerate kinase is particularly relevant to our understanding of phosphate-transfer mechanisms. The question of the relation between structure in the solid and solution is still with us and n.m.r. has proved to be the best way to study the differences and similarities. M any enzyme substrate complexes have been ‘mapped’ in solution, by using the perturbation of the n.m.r. spectra by param agnetic centres as a measure of interatomic distances. How such results can lead to both structural and mechanistic information will be discussed by Dr Mildvan. To understand mechanisms we must also get some information about the nature of transition states. Here, stereochemical observations play an important role and Dr Lowe will describe some elegant work on the use of chiral phosphates in approaching this problem. Finally, it is important to describe structures, intermediates and transition states in terms of the kinetic behaviour of the enzyme and Dr Dalziel will give us an example of both steady-state and pre-steady-state rate studies. Measurements of reaction rates ultimately link studies on the isolated enzyme to their behaviour in vivo . As this last step in the sequence is not covered by the formal presentations at this meeting I should like to show briefly how n.m.r. can now be used to obtain fluxes of enzyme catalysed reactions in vivo both in the steady state and at equilibrium.