Peptidylglycine alpha-amidating reaction: evidence for a two-step mechanism involving a stable intermediate at neutral pH

In our previous study of the rat brain alpha-amidating activity, we suggested that a protein of 41 kdal (41K protein) that shows no alpha-amidating activity is required for the reaction at neutral pH in addition to an alpha-amidating enzyme of 36 kdal (36K enzyme). Here we report on the purification of both proteins to near homogeneity and provide evidence that alpha-amidation proceeds via a two-step mechanism involving a stable intermediate at neutral pH, which is initially formed by the 36K enzyme and then readily converted into an amide product by the 41K protein.