<i>myo</i>‐Inositol oxygenase from rat kidneys

Koller, Franz; Koller, Elisabeth

doi:10.1111/j.1432-1033.1990.tb19355.x

Cited by 10 publications

(3 citation statements)

References 32 publications

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“…In addition, this analysis revealed that rMIOX did not dimerize on the addition of myoinositol or myo-inositol plus Fe# + \cysteine to the enzyme. This is in contrast with the substrate-dependent oligomerization reported previously [35] for the rat kidney native MIOX. An isoelectric focusing gel was run with two sets of standards (Sigma).…”

Section: Figure 5 Substrate Kinetics Of the Oxidation Of Myo-inositolcontrasting

confidence: 99%

“…Thus there is a considerable discrepancy between the subunit molecular mass of the native enzyme from rat kidney (17 kDa) and the predicted value from the reported hypothetical rat transcript, which is approximately double the size [34]. Our results with pig rMIOX prove convincingly that the pig protein has a molecular mass of 32.7 kDa and, in contrast with Koller's observations [35,37,38], does not undergo oligomerization in the presence of myo-inositol.…”

Section: Discussioncontrasting

confidence: 74%

“…Although the authors reported it as a protein of the aldehyde reductase (ALR) family, it is conceivable that it could be MIOX. However, if this hypothetical protein in rat is indeed MIOX, this needs to be reconciled with the work of Koller and colleagues [35,37,38], who have extensively characterized the rat enzyme and shown MIOX to be an oligomer of 17 kDa subunits. Thus there is a considerable discrepancy between the subunit molecular mass of the native enzyme from rat kidney (17 kDa) and the predicted value from the reported hypothetical rat transcript, which is approximately double the size [34].…”

Section: Discussionmentioning

confidence: 99%

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myo-Inositol oxygenase: molecular cloning and expression of a unique enzyme that oxidizes myo-inositol and d-chiro-inositol

et al. 2001

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myo-Inositol oxygenase (MIOX) catalyses the first committed step in the only pathway of myo-inositol catabolism, which occurs predominantly in the kidney. The enzyme is a non-haem-iron enzyme that catalyses the ring cleavage of myo-inositol with the incorporation of a single atom of oxygen. A full-length cDNA was isolated from a pig kidney library with an open reading frame of 849 bp and a corresponding protein subunit molecular mass of 32.7 kDa. The cDNA was expressed in a bacterial pET expression system and an active recombinant MIOX was purified from bacterial lysates to electrophoretic homogeneity. The purified enzyme displayed the same catalytic properties as the native enzyme with K(m) and k(cat) values of 5.9 mM and 11 min(-1) respectively. The pI was estimated to be 4.5. Preincubation with 1 mM Fe(2+) and 2 mM cysteine was essential for the enzyme's activity. D-chiro-Inositol, a myo-inositol isomer, is a substrate for the recombinant MIOX with an estimated K(m) of 33.5 mM. Both myo-inositol and D-chiro-inositol have been implicated in the pathogenesis of diabetes. Thus an understanding of the regulation of MIOX expression clearly represents a potential window on the aetiology of diabetes as well as on the control of various intracellular phosphoinositides and key signalling pathways.

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Section: Figure 5 Substrate Kinetics Of the Oxidation Of Myo-inositolcontrasting

confidence: 99%

Section: Discussioncontrasting

confidence: 74%

Section: Discussionmentioning

confidence: 99%

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myo-Inositol oxygenase: molecular cloning and expression of a unique enzyme that oxidizes myo-inositol and d-chiro-inositol

et al. 2001

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Purification, characterization and functional cloning of inositol oxygenase from Cryptococcus

Kanter

Becker

Friauf

et al. 2003

Yeast

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The enzyme inositol oxygenase (myo-inositol : oxygen oxidoreductase; E.C. 1.13.99.1) is a monooxygenase that converts inositol into glucuronic acid in the presence of molecular oxygen. This enzyme is integrated into a pathway leading to either degradation and energy production or the biosynthesis of precursors for polysaccharides. The enzyme was purified from the yeast Cryptococcus lactativorus by a five-step chromatography procedure. The purified enzyme shows a molecular mass of 37 kDa on SDS-PAGE, similar to the estimation of the size of the native enzyme determined by size exclusion chromatography. Peptides of the inositol oxygenase protein derived from a tryptic digest were sequenced de novo by nanoelectrospray tandem mass spectrometry. Using degenerate oligonucleotides, the corresponding gene was cloned from first strand cDNA. The open reading frame encodes a 315 amino acid polypeptide with a predicted molecular mass of 36.9 kDa. Inositol oxygenase is a single copy gene in C. lactativorus. It has close homologues in other fungi such as Cryptococcus neoformans and Neurospora crassa. Biochemical characterization of the enzyme showed a pH optimum of 6-6.5 and a temperature optimum of 30• C. Myo-inositol is the only accepted substrate with a K m of ca. 5 mM. The enzyme contains a Fe-centre but the enzyme activity is resistant to KCN.

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Inositol oxygenase

Springer Handbook of Enzymes

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myo‐Inositol oxygenase from rat kidneys

Cited by 10 publications

References 32 publications

myo-Inositol oxygenase: molecular cloning and expression of a unique enzyme that oxidizes myo-inositol and d-chiro-inositol

myo-Inositol oxygenase: molecular cloning and expression of a unique enzyme that oxidizes myo-inositol and d-chiro-inositol

Purification, characterization and functional cloning of inositol oxygenase from Cryptococcus

Inositol oxygenase

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