Structures of glutamine amidotransferases from the purine biosynthetic pathway.

Introduction Glutamine is the source for most of the nitrogen in biosynthetic pathways because of its connection to carbohydrate metabolism via cr-oxoglutarate and glutamate. The enzymes that transfer nitrogen from the amide of glutamine to acceptor substrates in biosynthetic pathways are known as glutamine amidotransferases. Glutamine amidotransferases are a large and well studied family of enzymes for which the first three-dimensional structures have recently been determined. This paper summarizes the structural information on glutamine amidotransferases and places it in the context of existing biochemical data on the enzymes . The fundamental reaction catalysed by glutamine amidotransferases is: