The GHMP class of small metabolite kinases participates in several essential metabolic processes, such as glycolysis, amino acid biosynthesis, and sterol biosynthesis. Currently, the GHMP superfamily contains more than 170 proteins, representing about 12-13 different functions, including galactokinases, homoserine kinases, mevalonate kinases, phosphomevalonate kinases (hence GHMP), mevalonate diphosphate decarboxylase, isopentenyl monophosphate kinase, and archaeal shikimate kinase. Deficiencies in GHMP enzyme activities cause auxotrophic phenotypes in bacteria and hereditary metabolic diseases in humans. Structural characterization of GHMP enzymes and their complexes with substrates is crucial for understanding the active site, catalytic mechanism, inhibition and regulation of these enzymes. The first three dimensional structure of a GHMP protein, the homoserine kinase (HK), revealed a novel nucleotide-binding fold and a unique ATP binding mode. The crystals of the ternary complex between HK and its substrates were also obtained. Structural analysis of the HK-substrate complexes will reveal the key catalytic residues in the phosphoryl transfer reaction and the residues responsible for the substrate specificity. To learn how GHMP-fold accommodates substrates of very different structures, other members in the GHMP superfamily are selected for the structural studies in a systematic approach. Diffracting crystals of the archaeal shikimate kinase have been obtained. Comparative analysis of the enzyme-substrate complexes from different members of the GHMP superfamily will reveal the structural determinants of the substrate specificity in each family, provide a foundation for the structure-base drug design, and further our understanding of the structure-function evolution of this important class of enzymes.
