In order to advance our understanding of the chemistry and biology of the greater family of manganese- requiring enzymes, we propose to explore structure-function relationships in human arginase I as well as the arginase-related metalloenzymes histone deacetylase 8 and polyamine deacetylase. Human arginase I contains a binuclear manganese cluster required for the hydrolysis of L-arginine to form L-ornithine and urea, and our studies indicate that catalysis proceeds through a mechanism in which both metal ions function to activate a metal-bridging hydroxide ion as the catalytic nucleophile. We have determined the structure of this enzyme to 1.29 ? resolution, and we will use this structure to guide the design of inhibitors and biosensors. Recent discoveries show that arginase is upregulated in various diseases such as atherosclerosis, asthma, and cancer, so our studies will expand the repertoire of chemical compounds that will potentially be useful for the treatment and diagnosis of human disease. Given the newly-discovered and unexpected structural relationship between the arginases and metal- dependent deacetylases, our structural and functional studies will illuminate important mechanistic parallels between these enzyme families. Intriguingly, the Zn2+ site of the deacetylase corresponds to the Mn2+B site of arginase, but the deacetylase does not contain a metal binding site corresponding to Mn2+A of arginase. Thus, the stoichiometry of metal binding has diverged in the evolution of the arginases and the deacetylases from a common metalloenzyme precursor. Intriguingly, the biologically preferred metal ion of human histone deacetylase-8 is believed to be Fe2+. Therefore, we will determine the structures of the Fe2+-substituted enzyme, its site-specific variants, and its substrate and inhibitor complexes. Since this enzyme is a validated drug target for cancer chemotherapy, it is important to thoroughly understand structure-function relationships in the form of the metalloenzyme that is found in vivo. Overall, the proposed research will provide a greater structural and functional understanding of metal ion specificity (Mn2+, Zn2+, Fe2+) and stoichiometry in the evolution of the arginases and the arginase-related deacetylases.

Public Health Relevance

Structural and functional studies of human arginase I, human histone deacetylase-8, and bacterial polyamine deacetylase will facilitate the design of potential new drugs that can be used to treat atherosclerosis, asthma, and cancer. Additionally, our studies will enable the design and development of biosensors that may be useful in the early diagnosis of human disease.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Macromolecular Structure and Function A Study Section (MSFA)
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Smith, Ward
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University of Pennsylvania
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Gantt, Sister M Lucy; Decroos, Christophe; Lee, Matthew S et al. (2016) General Base-General Acid Catalysis in Human Histone Deacetylase 8. Biochemistry 55:820-32
Porter, Nicholas J; Christianson, Nicolas H; Decroos, Christophe et al. (2016) Structural and Functional Influence of the Glycine-Rich Loop G(302)GGGY on the Catalytic Tyrosine of Histone Deacetylase 8. Biochemistry 55:6718-6729
Hai, Yang; Christianson, David W (2016) Histone deacetylase 6 structure and molecular basis of catalysis and inhibition. Nat Chem Biol 12:741-7
Hai, Yang; Christianson, David W (2016) Crystal structures of Leishmania mexicana arginase complexed with α,α-disubstituted boronic amino-acid inhibitors. Acta Crystallogr F Struct Biol Commun 72:300-6
Decroos, Christophe; Christianson, David W (2015) Design, Synthesis, and Evaluation of Polyamine Deacetylase Inhibitors, and High-Resolution Crystal Structures of Their Complexes with Acetylpolyamine Amidohydrolase. Biochemistry 54:4692-703
Hai, Yang; Kerkhoven, Eduard J; Barrett, Michael P et al. (2015) Crystal structure of an arginase-like protein from Trypanosoma brucei that evolved without a binuclear manganese cluster. Biochemistry 54:458-71
Decroos, Christophe; Christianson, Nicolas H; Gullett, Laura E et al. (2015) Biochemical and structural characterization of HDAC8 mutants associated with Cornelia de Lange syndrome spectrum disorders. Biochemistry 54:6501-13
Decroos, Christophe; Clausen, Dane J; Haines, Brandon E et al. (2015) Variable active site loop conformations accommodate the binding of macrocyclic largazole analogues to HDAC8. Biochemistry 54:2126-35
Hai, Yang; Edwards, Jennifer E; Van Zandt, Michael C et al. (2014) Crystal structure of Schistosoma mansoni arginase, a potential drug target for the treatment of schistosomiasis. Biochemistry 53:4671-84
Hai, Yang; Dugery, Reilly Jane; Healy, David et al. (2013) Formiminoglutamase from Trypanosoma cruzi is an arginase-like manganese metalloenzyme. Biochemistry 52:9294-309

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