ABSTRACT
The most frequent of the domain structures are the alpha/beta (a/b) domains, which consist of a central parallel or mixed b sheet surrounded by a helices. All the glycolytic enzymes are a/b structures as are many other enzymes as well as proteins that bind and transport metabolites. In a/b domains, binding crevices are formed by loop regions. These regions do not contribute to the structural stability of the fold but participate in binding and catalytic action.
