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PubMed1991

[Malignant hyperthermia and inositol phosphate metabolism in the heart and skeletal musculature].

There are recent reports that inositol phosphate metabolism is involved in the development of malignant hyperthermia (MH). Consequently, we investigated the basal concentration of inositol phosphate products in skeletal and heart muscles of malignant hyperthermia-susceptible (MHS) and healthy control (MHN) swine. Different inositol phosphates were measured by high pressure liquid chromatography, including inositol trisphosphate, tetrakisphosphate, pentakisphosphate and hexakisphosphate. All inositol phosphate products measured had a higher concentration in MHS than MHN in skeletal (304-1330%) as well as heart muscles (134-440%). An activation of the inositol phosphate metabolism has been shown to mobilise intracellular calcium from the sarcoplasmic reticulum. It is therefore concluded that, firstly, besides involvement of the skeletal muscles a primary myocardial abnormality in MHS is possible; and secondly, the idea that the inositol phosphate metabolism could be involved in the development of MH is additionally supported.

Animals↗
PubMed2002

Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells.

OBJECTIVE: The purpose of this study was to determine the effects of magnesium sulfate on inositol trisphosphate production and the mechanism of these effects. STUDY DESIGN: Myometrium was obtained at the time of cesarean delivery from women before labor at term. Inositol trisphosphate was measured in the primary myometrial cell cultures after stimulation with oxytocin, sodium fluoride, or Bay K 8644 with or without preincubation with magnesium sulfate or nifedipine. Experiments were performed in either calcium-containing or calcium-free medium that contained egtazic acid and after preincubation with the intracellular calcium chelator BAPTA-acetoxymethylester. Inositol trisphosphate production was measured by radioreceptor assay. In separate experiments, changes in intracellular calcium concentrations ([Ca(2+)](i)) were measured with the use of Fura-2 and spectrophotofluorometry. RESULTS: Oxytocin, sodium fluoride, and Bay K 8644 increased inositol trisphosphate production 2- to 4-fold. Preincubation with magnesium sulfate (3 x 10(-3) mol/L) for > or = 5 minutes decreased oxytocin-, sodium fluoride-, and Bay K 8644-induced inositol trisphosphate production in either calcium-containing or calcium-free media. Preincubation with BAPTA-acetoxymethylester decreased oxytocin-stimulated inositol trisphosphate production by 78% in calcium-containing media and completely prevented the oxytocin response in calcium-free media. Magnesium sulfate decreased inositol trisphosphate production in calcium-containing media but had no additional effect in calcium-free media. Oxytocin and Bay K 8644 increased [Ca(2+)](i) in either calcium-containing or calcium-free media, and magnesium sulfate reduced this in both cases. CONCLUSION: Magnesium sulfate appears to inhibit phosphatidylinositol-4, 5-bisphosphate-specific phospholipase C activity and subsequent calcium release in cultured myometrial cells by a direct effect on phospholipase C.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1996

Isolation of inositol 1,3,4-trisphosphate 5/6-kinase, cDNA cloning and expression of the recombinant enzyme.

Inositol 1,3,4-trisphosphate 5/6-kinase was purified 12,900-fold from calf brain using chromatography on heparin-agarose and affinity elution with inositol hexakisphosphate. The final preparation contained proteins of 48 and 36-38 kDa. All of these proteins had the same amino-terminal sequence and were enzymatically active. The smaller species represent proteolysis products with carboxyl-terminal truncation. The Km of the enzyme for inositol 1,3,4-trisphosphate was 80 nM with a Vmax of 60 nmol of product/min/mg of protein. The amino acid sequence of the tryptic peptide HSKLLARPAGGLVGERTCNAXP matched the protein sequence encoded by a human expressed sequence tag clone (GB T09063) at 16 of 22 residues. The expressed sequence tag clone was used to screen a human fetal brain cDNA library to obtain a cDNA clone of 1991 base pairs (bp) that predicts a protein of 46 kDa. The clone encodes the amino-terminal amino acid sequence obtained from the purified calf brain preparation, suggesting that it represents its human homologue. The cDNA was expressed as a fusion protein in Escherichia coli and was found to have inositol 1,3,4-trisphosphate 5/6-kinase activity. Remarkably, both the purified calf brain and recombinant proteins produced both inositol 1,3,4,6-tetrakisphosphate and inositol 1,3,4,5-tetrakisphosphate as products in a ratio of 2.3-5:1. This finding proves that a single kinase phosphorylates inositol in both the D5 and D6 positions. Northern blot analysis identified a transcript of 3.6 kilobases in all tissues with the highest levels in brain. The composite cDNA isolated contains 3054 bp with a poly(A) tail, suggesting that 500-600 bp of 5' sequence remains to be identified.

Amino Acid Sequence↗
PubMed2003

Regulation of phosphatidylglycerophosphate synthase by inositol in Saccharomyces cerevisiae is not at the level of PGS1 mRNA abundance.

Phosphatidylglycerophosphate synthase catalyzes the committed step in the synthesis of the mitochondrial phospholipid cardiolipin. We showed previously that phosphatidylglycerophosphate synthase activity in Saccharomyces cerevisiae is increased in conditions favoring mitochondrial development and during growth in the absence of inositol. Interestingly, the regulatory effects of inositol were not altered in ino2, ino4, or opi1 mutants suggesting that regulation in response to inositol is not at the level of gene transcription. We report here that steady state mRNA levels of the PGS1 gene, which encodes phosphatidylglycerophosphate synthase, were not altered by inositol or choline. Growth in the presence of the inositol-depleting drug valproate led to an increase in phosphatidylglycerophosphate synthase activity unaccompanied by increased PGS1 mRNA. PGS1 mRNA abundance was not decreased in ino2 or ino4 mutants and was unaffected in an opi1 mutant. Therefore, regulation of phosphatidylglycerophosphate synthase by inositol is not mediated at the level of mRNA abundance and does not require the INO2-INO4-OPI1 regulatory circuit. PGS1 was increased in glycerol/ethanol compared with glucose media and was maximally expressed as cells entered the stationary phase. Deletion of the mitochondrial genome did not affect PGS1 expression. Thus, whereas inositol controls phosphatidylglycerophosphate synthase activity, regulation of PGS1 expression occurs primarily in response to mitochondrial development cues.

Blotting, Northern↗
PubMed2004

Inositol deacylation of glycosylphosphatidylinositol-anchored proteins is mediated by mammalian PGAP1 and yeast Bst1p.

The inositol moiety of mammalian glycosylphosphatidylinositol (GPI) is acylated at an early step in GPI biosynthesis. The inositol acylation is essential for the generation of mature GPI capable of attachment to proteins. However, the acyl group is usually absent from GPI-anchored proteins (GPI-APs) on the cell surface due to inositol deacylation that occurs in the endoplasmic reticulum (ER) soon after GPI-anchor attachment. Mammalian GPI inositol-deacylase has not been cloned, and the biological significance of the deacylation has been unclear. Here we report a GPI inositol-deacylase-deficient Chinese hamster ovary cell line established by taking advantage of resistance to phosphatidylinositol-specific phospholipase C and the gene responsible, which was termed PGAP1 for Post GPI Attachment to Proteins 1. PGAP1 encoded an ER-associated, 922-amino acid membrane protein bearing a lipase consensus motif. Substitution of a conserved putative catalytic serine with alanine resulted in a complete loss of function, indicating that PGAP1 is the GPI inositol-deacylase. The mutant cells showed a clear delay in the maturation of GPI-APs in the Golgi and accumulation of GPI-APs in the ER. Thus, the GPI inositol deacylation is important for efficient transport of GPI-APs from the ER to the Golgi.

Acylation↗
PubMed2004

Regulation of casein kinase-2 (CK2) activity by inositol phosphates.

Casein kinase 2 (CK2) was one of the first protein kinases to be discovered and has been suggested to be responsible for as much as one-fifth of the eukaryotic phosphoproteome. Despite being responsible for the phosphorylation of a vast array of proteins central to numerous dynamic cellular processes, the activity of CK2 appears to be unregulated. In the current study, we identified a protein kinase activity in rat liver supernatant that is up-regulated by inositol 1,3,4,5-tetrakisphosphate (IP4) and inositol hexakisphosphate (IP6). The substrate for the inositol phosphate-regulated protein kinase was identified as a phosphatidylcholine transfer protein-like protein. Using the phosphorylation of this substrate in an assay, we purified the inositol phosphate-regulated protein kinase and determined it to be CK2. Bacterially expressed recombinant CK2, however, showed very high basal activity and was only modestly activated by IP6 and not regulated by IP. We found that an endogenous component present in rat liver supernatant was able to inhibit both recombinant and liver-purified CK2 basal activity. Under these conditions, recombinant CK2 catalytic activity could be increased substantially by IP4, inositol 1,3,4,5,6-pentakisphosphate (IP5), and IP6. We concluded that, contrary to the previously held view, CK2 can exist in a state of low constitutive activity allowing for its regulation by inositol phosphates. The ability of the higher inositol phosphates to directly stimulate CK2 catalytic activity provides the first evidence that these signaling molecules can operate via a direct control of protein phosphorylation.

Amino Acid Sequence↗
PubMed2006

Removal or maintenance of inositol-linked acyl chain in glycosylphosphatidylinositol is critical in trypanosome life cycle.

The protozoan parasite Trypanosoma brucei is coated by glycosylphosphatidylinositol (GPI)-anchored proteins. During GPI biosynthesis, inositol in phosphatidylinositol becomes acylated. Inositol is deacylated prior to attachment to variant surface glycoproteins in the bloodstream form, whereas it remains acylated in procyclins in the procyclic form. We have cloned a T. brucei GPI inositol deacylase (GPIdeAc2). In accordance with the acylation/deacylation profile, the level of GPIdeAc2 mRNA was 6-fold higher in the bloodstream form than in the procyclic form. Knockdown of GPIdeAc2 in the bloodstream form caused accumulation of an inositol-acylated GPI, a decreased VSG expression on the cell surface and slower growth, indicating that inositol-deacylation is essential for the growth of the bloodstream form. Overexpression of GPIdeAc2 in the procyclic form caused an accumulation of GPI biosynthetic intermediates lacking inositol-linked acyl chain and decreased cell surface procyclins because of release into the culture medium, indicating that overexpression of GPIdeAc2 is deleterious to the surface coat of the procyclic form. Therefore, the GPI inositol deacylase activity must be tightly regulated in trypanosome life cycle.

Acylation↗
PubMed2002

D-chiro-inositol--its functional role in insulin action and its deficit in insulin resistance.

In this review we discuss the biological significance of D-chiro-inositol, originally discovered as a component of a putative mediator of intracellular insulin action, where as a putative mediator, it accelerates the dephosphorylation of glycogen synthase and pyruvate dehydrogenase, rate limiting enzymes of non-oxidative and oxidative glucose disposal. Early studies demonstrated a linear relationship between its decreased urinary excretion and the degree of insulin resistance present. When tissue contents, including muscle, of type 2 diabetic subjects were assayed, they demonstrated a more general body deficiency. Administration of D-chiro-inositol to diabetic rats, Rhesus monkeys and now to humans accelerated glucose disposal and sensitized insulin action. A defect in vivo in the epimerization of myo-inositol to chiro-inositol in insulin sensitive tissues of the GK type 2 diabetic rat has been elucidated. Thus, administered D-chiro-inositol may act to bypass a defective normal epimerization of myo-inositol to D-chiro-inositol associated with insulin resistance and act to at least partially restore insulin sensitivity and glucose disposal.

Animals↗
PubMed2003

PIG-W is critical for inositol acylation but not for flipping of glycosylphosphatidylinositol-anchor.

Many cell surface proteins are anchored to a membrane via a glycosylphosphatidylinositol (GPI), which is attached to the C termini in the endoplasmic reticulum. The inositol ring of phosphatidylinositol is acylated during biosynthesis of GPI. In mammalian cells, the acyl chain is added to glucosaminyl phosphatidylinositol at the third step in the GPI biosynthetic pathway and then is usually removed soon after the attachment of GPIs to proteins. The mechanisms and roles of the inositol acylation and deacylation have not been well clarified. Herein, we report derivation of human and Chinese hamster mutant cells defective in inositol acylation and the gene responsible, PIG-W. The surface expressions of GPI-anchored proteins on these mutant cells were greatly diminished, indicating the critical role of inositol acylation. PIG-W encodes a 504-amino acid protein expressed in the endoplasmic reticulum. PIG-W is most likely inositol acyltransferase itself because the tagged PIG-W affinity purified from transfected human cells had inositol acyltransferase activity and because both mutant cells were complemented with PIG-W homologs of Saccharomyces cerevisiae and Schizosaccharomyces pombe. The inositol acylation is not essential for the subsequent mannosylation, indicating that glucosaminyl phosphatidylinositol can flip from the cytoplasmic side to the luminal side of the endoplasmic reticulum.

Acylation↗
PubMed1999

Inositol phosphates with different numbers of phosphate groups influence iron absorption in humans.

BACKGROUND: Inositol hexaphosphate (IP(6)) is a well-known inhibitor of iron absorption, whereas the effects of the less-phosphorylated derivatives of IP(6) are less known. OBJECTIVES: The objective was to investigate the effects of inositol tri-, tetra-, and pentaphosphates (IP(3), IP(4), and IP(5), respectively) on iron absorption in humans. DESIGN: Iron absorption was measured in 5 experiments from single meals by extrinsic labeling with (55)Fe and (59)Fe and determination of whole-body retention and the erythrocyte uptake of isotopes. In experiments 1-3 the meals contained white-wheat rolls to which 10 mg P as IP(5), IP(4), or IP(3), respectively, was added. Inositol 1,2,6-triphosphate [Ins(1,2, 6)P(3)] and a mixture of isomers of IP(4) and IP(5) were studied. White-wheat rolls contained 10 mg P as IP(3) + IP(4) and 2 mg P as IP(5) + IP(6) in experiment 4 and 20 mg P as IP(3) + IP(4) and 3 mg P as IP(5) + IP(6) in experiment 5; inositol phosphates were obtained via fermentation of sodium phytate. Each experiment had 8-11 subjects. RESULTS: In experiment 1, iron absorption was reduced by 39%, whereas there was no significant effect on iron absorption in experiments 2 and 3. In experiments 4 and 5, iron absorption was reduced by 54% and 64%, respectively, suggesting that IP(3) and IP(4) contributed to the inhibitory effect. CONCLUSIONS: IP(5) has an inhibitory effect on iron absorption, whereas IP(3) and IP(4) in isolated form have no such effect. IP(3) and IP(4) in processed food contribute to the negative effect on iron absorption, presumably by binding iron between different inositol phosphates. To improve iron absorption from cereals and legumes, degradation of inositol phosphates needs to be to less-phosphorylated inositol phosphates than IP(3).

Absorption↗
PubMed1991

Ion chromatographic determination of inositol tris- and tetrakisphosphates in rat brain.

Ion chromatography has been applied to the determination of inositol 2,4,5-trisphosphate (Ins 2,4,5-P3), inositol 1,3,4-trisphosphate (Ins 1,3,4-P3), inositol 1,4,5-trisphosphate (Ins 1,4,5-P3), and inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5-P4). Other common polyanionic metabolites, including ATP and GTP, do not interfere with the determinations even at concentrations exceeding those normally found in tissue extracts. Assay of rat brain for Ins 1,4,5-P3 and Ins 1,3,4,5-P4 by the method of standard addition gives values which are within 10% of the amount calculated by external calibration. When rat brain homogenates are spiked with Ins 1,4,5-P3, the recoveries are greater than 90%. Treatment of animals with lithium chloride and pilocarpine produces increases in total inositol trisphosphates from 14 to 64 nMol/g wet weight, and increases in Ins 1,3,4,5-P4 from 0.9 to 18 nMol/g wet weight in tissue extracts obtained from the cerebral cortex. Using chemically suppressed conductivity, detection limits in brain are estimated to be 50 pMol/g wet weight for inositol trisphosphates and 22 pMol/g wet weight for inositol tetrakisphosphate.

Adenosine Triphosphate↗
PubMed2003

Specific isoforms of protein kinase C are essential for prevention of folate-resistant neural tube defects by inositol.

A proportion of neural tube defects (NTDs) can be prevented by maternal folic acid supplementation, although some cases are unresponsive. The curly tail mutant mouse provides a model of folate-resistant NTDs, in which defects can be prevented by inositol therapy in early pregnancy. Hence, inositol represents a possible novel adjunct therapy to prevent human NTDs. The present study investigated the molecular mechanism by which inositol prevents mouse NTDs. Activation of protein kinase C (PKC) is known to be essential, and we examined neurulation-stage embryos for PKC expression and applied PKC inhibitors to curly tail embryos developing in culture. Although all known PKC isoforms were detected in the closing neural tube, use of chemical PKC inhibitors identified a particular requirement for 'conventional' PKC isoforms. Peptide inhibitors offer selective inhibition of individual PKCs, and we demonstrated isoform-specific inhibition of PKC in embryonic cell cultures. Application of peptide inhibitors to neurulation-stage embryos revealed an absolute dependence on the activity of PKCbetaI and gamma for prevention of NTDs by inositol, and partial dependence on PKCzeta, whereas other PKCs (alpha, betaII delta, and epsilon) were dispensable. To investigate the cellular action of inositol and PKCs in NTD prevention, we examined cell proliferation in curly tail embryos. Defective proliferation of hindgut cells is a key component of the pathogenic sequence leading to NTDs in curly tail. Hindgut cell proliferation was stimulated specifically by inositol, an effect that required activation of PKCbetaI. Our findings reveal an essential role of specific PKC isoforms in mediating the prevention of mouse NTDs by inositol.

Animals↗
PubMed1976

The influence of dietary inositol on glyceride composition and synthesis in livers of rats fed different fats.

The effect of inositol supplementation on the composition and biosynthesis of glycerides in the livers of rats fed diets containing fats with differing fatty acid composition was investigated. The dietary fats employed in these studies included corn oil, Tower rapeseed oil (RSO), partially hydrogenated soybean oil (SBO), and tallow. No significant influence of inositol on hepatic triglyceride levels was found in animals fed corn oil and SBO whereas inositol deficiency caused a two-and four-fold elevation in triglyceride concentrations in the RSO and tallow groups, respectively. The level of total fatty acids in phospholipid (mg/g liver) was slightly decreased in all fat groups and included a notable decrease in the concentration of monoenoic (18:1) and dienoic (18:2) acids in the RSO and tallow groups. Dietary inositol had a minor effect on the weight % of individual fatty acids in hepatic triglycerides. Inositol-deficient animals showed an increased rate of glyceride synthesis from glycerol-3-phosphate (glycerol-3-P) regardless of the type of fat that was fed. The results indicate that triglyceride accumulation in liver under conditions of inositol deficiency is not only produced with highly saturated fats since the most unsaturated of all the fats tested, Tower RSO, also gave the syndrome. The results further suggested that the accumulation of hepatic lipid due to the feeding of inositol-deficient diets likely arises from their effect on specific metabolic site(s) other than the conversion of glycerol-3-P into lipid.

Animals↗
PubMed1990

Orthovanadate and fluoroaluminate stimulate inositol phosphate production and in vitro ovulation in goldfish (Carassius auratus) follicles.

Both sodium orthovanadate and fluoroaluminate were found to stimulate in vitro ovulation in intact goldfish follicles, suggesting the involvement of G-proteins in ovulation. Although orthovanadate was able to stimulate cAMP production, it probably stimulates ovulation by some other mechanism since cAMP blocks ovulation in this species. These agents also stimulated the accumulation of labeled inositol phosphate in follicle walls. The time course of inositol phosphate production showed a slightly delayed and continuous accumulation for isomers of inositol mono-, bis-, and trisphosphates. No change was observed in inositol tetrakisphosphate levels over time. The accumulation of inositol phosphates in response to orthovanadate was also dose-dependent. Lithium chloride (10 mM) caused varying increases in the levels of most isomers and a decrease in ins-3,4-P2. Inositol phosphate production varied significantly with changes in the maturational stage of follicles. Peak production was observed in follicles 7-8 h after hCG treatment, which corresponds almost exactly with the time of ovulation. This correlation of maximal inositol phosphate production with the time of ovulation, along with the stimulation of ovulation by diacylglycerols, a phorbol ester, and the G-protein-stimulating agents, orthovanadate and fluoroaluminate, suggests a role for polyphosphatidylinositol hydrolysis in ovulation.

Aluminum↗
PubMed2001

Double-blind, controlled, crossover trial of inositol versus fluvoxamine for the treatment of panic disorder.

Only 70% of patients respond to current treatments for panic disorder, and many discontinue drugs because of side effects. myo-Inositol, a natural isomer of glucose and a precursor for the second-messenger phosphatidyl-inositol system, has previously been found superior to placebo in the treatment of depression, panic disorder, and obsessive-compulsive disorder (OCD), but a direct comparison with an established drug has never been performed. A double-blind, controlled, random-order crossover study was undertaken to compare the effect of inositol with that of fluvoxamine in panic disorder. Twenty patients completed 1 month of inositol up to 18 g/day and 1 month of fluvoxamine up to 150 mg/day. Improvements on Hamilton Rating Scale for Anxiety scores, agoraphobia scores, and Clinical Global Impressions Scale scores were similar for both treatments. In the first month, inositol reduced the number of panic attacks per week (mean and SD) by 4.0 (2) compared with a reduction of 2.4 (2) with fluvoxamine (p = 0.049). Nausea and tiredness were more common with fluvoxamine (p = 0.02 and p = 0.01, respectively). Because inositol is a natural compound with few known side effects, it is attractive to patients who are ambivalent about taking psychiatric medication. Continuing reports of inositol's efficacy in the treatment of depression, panic disorder, and OCD should stimulate replication studies.

Adolescent↗
PubMed2006

Lithium alters regional rat brain myo-inositol at 2 and 4 weeks: an ex-vivo magnetic resonance spectroscopy study at 18.8 T.

Lithium has been the mainstay of treatment for bipolar disorder. Early studies suggest that lithium acts via inositol depletion. This study assesses the effect of 1, 2 and 4 weeks of lithium treatment on myo-inositol concentrations across several brain regions. Thirty-six Sprague-Dawley rats were treated for 2 weeks with an intraperitoneal injection of either 1 mmol/kg/day, twice daily lithium chloride (n=18) or placebo (2 ml/kg of saline) (n=18). The rats were separated into three groups: 1 week, 2 weeks and 4 weeks. Brains were dissected into prefrontal, temporal and occipital cortical areas, as well as hippocampus, and analyzed at 18.8 T. Myo-inositol was quantified using the Chenomx Profiler software. Lithium did not alter myo-inositol concentrations at 1 week. A significant reduction exists in myo-inositol concentrations in lithium-treated rats at 2 and 4 weeks, across all four brain regions. Studies suggest brain region-specific alterations in myo-inositol concentrations among bipolar patients. Our findings suggest that lithium-induced reduction of myo-inositol is more global.

Animals↗
PubMed1988

Inositol phosphates: proliferation, metabolism and function.

After the initial discovery of receptor-linked generation of inositol(1,4,5)trisphosphate (Ins(1,4,5)P3) it was generally assumed that Ins(1,4,5)P3 and its proposed breakdown products inositol(1,4)bisphosphate (Ins(1,4)P2) and Ins1P, along with cyclic inositol monophosphate, were the only inositol phosphates found in significant amounts in animal cells. Since then, three levels of complexity have been introduced. Firstly, Ins(1,4,5)P3 can be phosphorylated to Ins(1,3,4,5)P4, and the subsequent metabolism of these two compounds has been found to be intricate and probably different between various tissues. The functions of Ins(1,4,5)P3 and Ins(1,3,4,5)P4 are almost certainly to regulate cytosolic Ca2+ concentrations, but the reasons for the labyrinth of the metabolic pathways after their deactivation by a specific 5-phosphatase remain obscure. Secondly, inositol pentakis- and hexakisphosphates have been found in many animal cells other than avian erythrocytes. It has been shown that their synthesis pathway is entirely separate from the inositol phosphates discussed above, both in terms of many of the isomers involved and probably in the subcellular localization; some possible functions of InsP5 and InsP6 are discussed here. Thirdly, cyclic inositol polyphosphates have been reported in stimulated tissues; the evidence for their occurrence in vivo and their possible physiological significance are also discussed.

Animals↗
PubMed2004

The fifth gene of the iol operon of Bacillus subtilis, iolE, encodes 2-keto-myo-inositol dehydratase.

The myo-inositol catabolism pathway of Bacillus subtilis has not been fully characterized but was proposed to involve step-wise multiple reactions that finally yielded acetyl-CoA and dihydroxyacetone phosphate. It is known that the iolABCDEFGHIJ operon is responsible for the catabolism of inositol. IolG catalyses the first step of myo-inositol catabolism, the dehydrogenation of myo-inositol, producing 2-keto-myo-inositol (inosose). The second step was thought to be the dehydration of inosose. Genetic and biochemical analyses of the iol genes led to the identification of iolE, encoding the enzyme for the second step of inositol catabolism, inosose dehydratase. The reaction product of inosose dehydratase was identified as D-2,3-diketo-4-deoxy-epi-inositol.

Bacillus subtilis↗