The Haloalkanoate Dehalogenase Superfamily The haloalkanoate dehalogenase superfamily (HADSF) is one of the largest and most ubiquitous enzyme families identified to date, with over 3,000 members in organisms ranging from bacteria to humans. Remarkable diversity of chemistry and function has emerged through evolution of the HAD catalytic scaffold. Despite the name, the dehalogenases, which catalyze carbon group transfer, represent a minute fraction of the family. All other known catalytic activities are directed at phosphoryl transfer. Numerous proteins from the HADSF are found in each organism (29 in E. coli and 58 in humans, for example) where they perform a diverse collection of novel physiological functions in primary and secondary metabolism, membrane transport, signal transduction, and nucleic acid repair. The objective of the work in the Allen lab is to define selected enzymes of the HAD superfamily in terms of structure, catalysis, and function. From this information we will also develop a strategy for structure/function assignment of unknown proteins within the family. The approaches defined and information gained from the HADSF can form the basis for the analysis of other superfamilies unveiled by the sequencing of entire genomes. In our overall approach each subclass or branch of the superfamily is utilized to explore a different aspect of the reaction catalyzed, revealing both the means of diversification within the family and basic principles of catalysis. This project is in collaboration with the laboratory of Debra Dunaway Mariano, University of New Mexico and supported by NIH grant GM 61099.