title: A unique hexokinase in Cryptosporidium parvum, an apicomplexan pathogen lacking the Krebs cycle and oxidative phosphorylation.
abstract: Cryptosporidium parvum may cause virtually untreatable infections in AIDS patients, and is recently identified as one of the top four diarrheal pathogens in children in developing countries. Cryptosporidium differs from other apicomplexans (e.g., Plasmodium and Toxoplasma) by lacking many metabolic pathways including the Krebs cycle and cytochrome-based respiratory chain, thus relying mainly on glycolysis for ATP production. Here we report the molecular and biochemical characterizations of a hexokinase in C. parvum (CpHK). Our phylogenetic reconstructions indicated that apicomplexan hexokinases including CpHK were highly divergent from those of humans and animals (i.e., at the base of the eukaryotic clade). CpHK displays unique kinetic features that differ from those in mammals and Toxoplasma gondii (TgHK) in the preference towards various hexoses and its capacity to use ATP and other NTPs. CpHK also displays substrate inhibition by ATP. Moreover, 2-deoxy-D-glucose (2DG) could not only inhibit the CpHK activity, but also the parasite growth in vitro at concentrations nontoxic to host cells (IC(50) = 0.54 mM). While the exact action of 2-deoxy-D-glucose on the parasite is subject to further verification, our data suggest that CpHK and the glycolytic pathway may be explored for developing anti-cryptosporidial therapeutics.
authors.affiliation: College of Veterinary Medicine, China Agricultural University, Haidian District, Beijing 100193, China; Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4467, USA.
authors.forename: Yonglan
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4467, USA.
authors.forename: Haili
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4467, USA.
authors.forename: Fengguang
authors.initials: F
authors.lastname: Guo
authors.affiliation: Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China.
authors.forename: Mingfei
authors.initials: M
authors.lastname: Sun
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4467, USA. Electronic address: gzhu@cvm.tamu.edu.
authors.forename: Guan
authors.initials: G
authors.lastname: Zhu
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D016000:Cluster Analysis; D016785:Cryptosporidium parvum / Q000201:enzymology* / Q000235:genetics*; D003847:Deoxyglucose; D004791:Enzyme Inhibitors / Q000378:metabolism; D006593:Hexokinase / Q000235:genetics* / Q000378:metabolism*; D006601:Hexoses / Q000378:metabolism; D020128:Inhibitory Concentration 50; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017385:Sequence Homology; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D006601:Hexoses; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; D006593:Hexokinase
keywords: 2-deoxy-D-glucose (2DG); Apicomplexan; Cryptosporidium parvum; Hexokinase; drug target.; substrate inhibition