In 1966, a paper entitled "On the formation of a novel adenylylic
compound by enzymatic extracts of liver nuclei" from Paul Mandel's
laboratory in Strasbourg, France, planted the seed for a rapidly growing
new field of biological research focusing on ADP-ribosylation reactions.
The development of this field over the past 2 decades reflects very much
a modern trend of biological research. As more detailed knowledge
accumulates, enigmatic phenomena turn into concepts which create their
own enigmata. This process tends to favor the development of multiple,
seemingly disconnected, research lines until simplicity emerges from
chaos and unifying concepts substitute for controversy. It appears that
the field of ADP-ribosylation reactions has not yet attained this latter
stage. For example, with the identification of two different classes of
ADP-ribosylation reactions, i.e., mono-ADP-ribosyla- tion and
poly-ADP-ribosylation reactions, the field split very early into two
separate branches of research. With the present volume, we have divided
the task of reviewing these two classes of ADP- ribosylation
accordingly, although their coexistence in eukaryotes may involve a
closer functional linkage than hitherto recognized.