ALPHA BETA BARREL EVOLUTION AND THE MODULAR ASSEMBLY OF ENZYMES - EMERGING TRENDS IN THE FLAVIN OXIDASE/DEHYDROGENASE FAMILY/

alpha/beta barrels have an ill-defined origin. Evidence exists which f avours their divergent evolution from a common ancestral barrel and co nvergent evolution to a stable fold. However, recent sequence and stru ctural information for the flavin oxidase/dehydrogenase family of barr el enzymes indicate that sub-families of alpha/beta barrels have evolv ed divergently. The modular fusion of barrel domains with core structu res from other gene families has also contributed to the evolution of related but catalytically distinct enzyme molecules within each sub-fa mily of the flavin oxidases/dehydrogenases. An analysis of the structu res and sequences of the flavin oxidases/dehydrogenases has now enable d studies focusing on the evolutionary origins and modular assembly of this important family of proteins to be initiated.