X-ray analysis has provided a 3-dimensional structural basis through which the complex processes of biochemistry and biology can be investigated and understood. The crystallographic studies on the serine hydrolases have provided accurate structures for many of the enzyme families and have shown that although the families evolved independently, their active atoms in their catalytic structures have equivalent stereochemistry. There has also been remarkable variation in the amino acid composition of the catalytic structures. Analysis has shown that their essential catalytic chemistry is achieved through the interactions of carboxyl or carbonyl oxygens, a base and a potential nucleophile. Finally the evolutionary changes in some enzyme families, such as the Ntn-hydrolases, are so extensive that their evolutionary relationships can only be detected by comparisons of their 3-dimensional structures. Thus X-ray analysis gives the biologist Chemical, functional and evolutionary insight into protein molecules
