title: Identification of purple acid phosphatase inhibitors by fragment-based screening: promising new leads for osteoporosis therapeutics.
abstract: Purple acid phosphatases are metalloenzymes found in animals, plants and fungi. They possess a binuclear metal centre to catalyse the hydrolysis of phosphate esters and anhydrides under acidic conditions. In humans, elevated purple acid phosphatases levels in sera are correlated with the progression of osteoporosis and metabolic bone malignancies, making this enzyme a target for the development of new chemotherapeutics to treat bone-related illnesses. To date, little progress has been achieved towards the design of specific and potent inhibitors of this enzyme that have drug-like properties. Here, we have undertaken a fragment-based screening approach using a 500-compound library identifying three inhibitors of purple acid phosphatases with K(i) values in the 30-60 μm range. Ligand efficiency values are 0.39-0.44 kcal/mol per heavy atom. X-ray crystal structures of these compounds in complex with a plant purple acid phosphatases (2.3-2.7 Å resolution) have been determined and show that all bind in the active site within contact of the binuclear centre. For one of these compounds, the phenyl ring is positioned within 3.5 Å of the binuclear centre. Docking simulations indicate that the three compounds fit into the active site of human purple acid phosphatases. These studies open the way to the design of more potent and selective inhibitors of purple acid phosphatases that can be tested as anti-osteoporotic drug leads.
authors.affiliation: School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Feder
authors.forename: Waleed M
authors.initials: WM
authors.lastname: Hussein
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Clayton
authors.forename: Meng-Wei
authors.initials: MW
authors.lastname: Kan
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schenk
authors.forename: Ross P
authors.initials: RP
authors.lastname: McGeary
authors.forename: Luke W
authors.initials: LW
authors.lastname: Guddat
mesh_terms: D000135:Acid Phosphatase / Q000037:antagonists & inhibitors* / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D006023:Glycoproteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D006801:Humans; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D010024:Osteoporosis / Q000188:drug therapy / Q000201:enzymology*; D027805:Phaseolus / Q000737:chemistry / Q000201:enzymology*; D013552:Swine
chemical_list: D004791:Enzyme Inhibitors; D006023:Glycoproteins; C091137:purple acid phosphatase; D000135:Acid Phosphatase