title: Structural elucidation of the NADP(H) phosphatase activity of staphylococcal dual-specific IMPase/NADP(H) phosphatase.
abstract: NADP(H)/NAD(H) homeostasis has long been identified to play a pivotal role in the mitigation of reactive oxygen stress (ROS) in the intracellular milieu and is therefore critical for the progression and pathogenesis of many diseases. NAD(H) kinases and NADP(H) phosphatases are two key players in this pathway. Despite structural evidence demonstrating the existence and mode of action of NAD(H) kinases, the specific annotation and the mode of action of NADP(H) phosphatases remains obscure. Here, structural evidence supporting the alternative role of inositol monophosphatase (IMPase) as an NADP(H) phosphatase is reported. Crystal structures of staphylococcal dual-specific IMPase/NADP(H) phosphatase (SaIMPase-I) in complex with the substrates D-myo-inositol-1-phosphate and NADP(+) have been solved. The structure of the SaIMPase-I-Ca(2+)-NADP(+) ternary complex reveals the catalytic mode of action of NADP(H) phosphatase. Moreover, structures of SaIMPase-I-Ca(2+)-substrate complexes have reinforced the earlier proposal that the length of the active-site-distant helix α4 and its preceding loop are the predisposing factors for the promiscuous substrate specificity of SaIMPase-I. Altogether, the evidence presented suggests that IMPase-family enzymes with a shorter α4 helix could be potential candidates for previously unreported NADP(H) phosphatase activity.
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India.
authors.forename: Sudipta
authors.initials: S
authors.lastname: Bhattacharyya
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India.
authors.forename: Anirudha
authors.initials: A
authors.lastname: Dutta
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India.
authors.forename: Debajyoti
authors.initials: D
authors.lastname: Dutta
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India.
authors.forename: Ananta Kumar
authors.initials: AK
authors.lastname: Ghosh
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Das
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007295:Inositol Phosphates / Q000737:chemistry; D008958:Models, Molecular; D009249:NADP / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013211:Staphylococcus aureus / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D007295:Inositol Phosphates; D009249:NADP; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D002118:Calcium
keywords: NADP(H) phosphatase; catalytic mechanism; crystal structure; folded conformation of NADP+; inositol monophosphatase; substrate specificity