Structural and biophysical characterization of human myo-inositol oxygenase. 2008

Ann-Gerd Thorsell, and Camilla Persson, and Nina Voevodskaya, and Robert D Busam, and Martin Hammarström, and Susanne Gräslund, and Astrid Gräslund, and B Martin Hallberg
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, SE-171 77 Stockholm, Sweden.

Altered inositol metabolism is implicated in a number of diabetic complications. The first committed step in mammalian inositol catabolism is performed by myo-inositol oxygenase (MIOX), which catalyzes a unique four-electron dioxygen-dependent ring cleavage of myo-inositol to D-glucuronate. Here, we present the crystal structure of human MIOX in complex with myo-inosose-1 bound in a terminal mode to the MIOX diiron cluster site. Furthermore, from biochemical and biophysical results from N-terminal deletion mutagenesis we show that the N terminus is important, through coordination of a set of loops covering the active site, in shielding the active site during catalysis. EPR spectroscopy of the unliganded enzyme displays a two-component spectrum that we can relate to an open and a closed active site conformation. Furthermore, based on site-directed mutagenesis in combination with biochemical and biophysical data, we propose a novel role for Lys(127) in governing access to the diiron cluster.

UI MeSH Term Description Entries
D007294 Inositol An isomer of glucose that has traditionally been considered to be a B vitamin although it has an uncertain status as a vitamin and a deficiency syndrome has not been identified in man. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1379) Inositol phospholipids are important in signal transduction. Myoinositol,Chiro-Inositol,Mesoinositol,Chiro Inositol
D010105 Oxygenases Oxidases that specifically introduce DIOXYGEN-derived oxygen atoms into a variety of organic molecules. Oxygenase
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D016296 Mutagenesis Process of generating a genetic MUTATION. It may occur spontaneously or be induced by MUTAGENS. Mutageneses
D017384 Sequence Deletion Deletion of sequences of nucleic acids from the genetic material of an individual. Deletion Mutation,Deletion Mutations,Deletion, Sequence,Deletions, Sequence,Mutation, Deletion,Mutations, Deletion,Sequence Deletions
D017434 Protein Structure, Tertiary The level of protein structure in which combinations of secondary protein structures (ALPHA HELICES; BETA SHEETS; loop regions, and AMINO ACID MOTIFS) pack together to form folded shapes. Disulfide bridges between cysteines in two different parts of the polypeptide chain along with other interactions between the chains play a role in the formation and stabilization of tertiary structure. Tertiary Protein Structure,Protein Structures, Tertiary,Tertiary Protein Structures
D048909 Diabetes Complications Conditions or pathological processes associated with the disease of diabetes mellitus. Due to the impaired control of BLOOD GLUCOSE level in diabetic patients, pathological processes develop in numerous tissues and organs including the EYE, the KIDNEY, the BLOOD VESSELS, and the NERVE TISSUE. Complications of Diabetes Mellitus,Diabetes-Related Complications,Diabetic Complications,Diabetes Complication,Diabetes Mellitus Complication,Diabetes Mellitus Complications,Diabetes Related Complications,Diabetes-Related Complication,Diabetic Complication
D050562 Inositol Oxygenase A non-heme IRON enzyme that catalyzes the conversion of MYOINOSITOL to D-glucuronic acid. The reaction is the first committed step in MYOINOSITOL catabolic pathway. This enzyme was formerly characterized as EC 1.13.1.11 and 1.99.2.6. Myo-Inositol Oxygenase,Myo Inositol Oxygenase,Oxygenase, Inositol,Oxygenase, Myo-Inositol

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