Rv2131c gene product: An unconventional enzyme that is both inositol monophosphatase and fructose-1,6-bisphosphatase

Gu, Xiaoling; Chen, Mao; Shen, Hongbo; Jiang, Xin; Huang, Yishu; Wang, Honghai

doi:10.1016/j.bbrc.2005.11.088

Cited by 22 publications

(31 citation statements)

References 29 publications

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“…SuhB was shown to have high activity with 1D-Ins-1-P, and lower activity with several other sugar phosphates, but activity with 1L-Ins-1-P was not tested (37). Similarly CysQ was recently reported to have IMP activity although only the 1D-isomer of Ins-1-P was apparently tested as substrate (38). The stereospecificity of IMPs from human (39), Escherichia coli, and A. fulgidus (40) has been examined with 1L-Ins-1-P and 1D-Ins-1-P and all were found to hydrolyze both substrates, so this may also be the case for the mycobacterial IMP.…”

Section: Discussionmentioning

confidence: 99%

Biochemistry of the Initial Steps of Mycothiol Biosynthesis

Newton

Bzymek

et al. 2006

Journal of Biological Chemistry

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Section: Discussionmentioning

confidence: 99%

Biochemistry of the Initial Steps of Mycothiol Biosynthesis

Newton

Bzymek

et al. 2006

Journal of Biological Chemistry

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“…Ins 2-P, pNPP, 2 -AMP, etc. The M.tuberculosis Rv2131c gene product has also been reported to be a bifunctional enzyme, belonging to the class-IV FBPase (Gu et al 2006). It also posseses a broader substrate specificity compared to several other Fig.…”

Section: Magnesium Dependence Of I-1-pase Activitymentioning

confidence: 98%

“…The IMPase proteins belong to a superfamily of metal dependent phosphatases with broad substrate specificity that includes synthetic substrates, cellular phosphorylated metabolites and some phosphorylated derivatives of inositol. Recently, the Rv2131c gene product of M. tuberculosis (Gu et al 2006) and inositol monophosphatases from Methanococcus jannaschii and Archaeoglobus fulgidus have also been shown to have Fructose 1,6-bisphosphatase activity (Stec et al 2000;Stieglitz et al 2002).…”

Section: Introductionmentioning

confidence: 96%

Functional identification of sll1383 from Synechocystis sp PCC 6803 as L-myo-inositol 1-phosphate phosphatase (EC 3.1.3.25): molecular cloning, expression and characterization

Patra

Dastidar

Maitra

et al. 2006

Planta

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The genome sequence of the cyanobacterium Synechocystis sp. PCC6803 revealed four Open reading frame (ORF) encoding putative inositol monophosphatase or inositol monophosphatase-like proteins. One of the ORFs, sll1383, is approximately 870 base pair long and has been assigned as a probable myo-inositol 1 (or 4) monophosphatase (IMPase; EC 3.1.3.25). IMPase is the second enzyme in the inositol biosynthesis pathway and catalyses the conversion of L-myo-inositol 1-phosphate to free myo-inositol. The present work describes the functional assignment of ORF sll1383 as myo-inositol 1-phosphate phosphatase (IMPase) through molecular cloning, bacterial overexpression, purification and biochemical characterization of the gene product. Affinity (K (m)) of the recombinant protein for the substrate DL-myo-inositol 1-phosphate was found to be much higher (0.0034 +/- 0.0003 mM) compared to IMPase(s) from other sources but in comparison V (max) ( approximately 0.033 mumol Pi/min/mg protein) was low. Li(+) was found to be an inhibitor (IC(50) 6.0 mM) of this enzyme, other monovalent metal ions (e.g. Na(+), K(+) NH (4) (+) ) having no significant effect on the enzyme activity. Like other IMPase(s), the activity of this enzyme was found to be totally Mg(2+) dependent, which can be substituted partially by Mn(2+). However, unlike other IMPase(s), the enzyme is optimally active at approximately 42 degrees C. To the best of our knowledge, sll1383 encoded IMPase has the highest substrate affinity and specificity amongst the known examples from other prokaryotic sources. A possible application of this recombinant protein in the enzymatic coupled assay of L-myo-inositol 1-phosphate synthase (MIPS) is discussed.

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“…The immediate product of the reaction of ino-1 is 1L-Ins-1-P, and the knockout mutant requires myo-inositol to produce phosphatidylinositol for cell wall synthesis. There are only two known types of enzymes that utilize inositol-1-phosphate in mycobacteria, i.e., inositol monophosphatase (SuhB [101,102] and CysQ [37,43]) and MshA. MshA cannot utilize myo-inositol or 1D-Ins-1-P, produced from the action of phospholipase C activity on phosphatidyinositol, to produce MSH (92).…”

Section: Fig 2 Biosynthesis Of Mshmentioning

confidence: 99%

Biosynthesis and Functions of Mycothiol, the Unique Protective Thiol of Actinobacteria

Newton

Buchmeier

Fahey

2008

Microbiol Mol Biol Rev

316

293

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SUMMARY Mycothiol (MSH; AcCys-GlcN-Ins) is the major thiol found in Actinobacteria and has many of the functions of glutathione, which is the dominant thiol in other bacteria and eukaryotes but is absent in Actinobacteria. MSH functions as a protected reserve of cysteine and in the detoxification of alkylating agents, reactive oxygen and nitrogen species, and antibiotics. MSH also acts as a thiol buffer which is important in maintaining the highly reducing environment within the cell and protecting against disulfide stress. The pathway of MSH biosynthesis involves production of GlcNAc-Ins-P by MSH glycosyltransferase (MshA), dephosphorylation by the MSH phosphatase MshA2 (not yet identified), deacetylation by MshB to produce GlcN-Ins, linkage to Cys by the MSH ligase MshC, and acetylation by MSH synthase (MshD), yielding MSH. Studies of MSH mutants have shown that the MSH glycosyltransferase MshA and the MSH ligase MshC are required for MSH production, whereas mutants in the MSH deacetylase MshB and the acetyltransferase (MSH synthase) MshD produce some MSH and/or a closely related thiol. Current evidence indicates that MSH biosynthesis is controlled by transcriptional regulation mediated by σB and σR in Streptomyces coelicolor. Identified enzymes of MSH metabolism include mycothione reductase (disulfide reductase; Mtr), the S-nitrosomycothiol reductase MscR, the MSH S-conjugate amidase Mca, and an MSH-dependent maleylpyruvate isomerase. Mca cleaves MSH S-conjugates to generate mercapturic acids (AcCySR), excreted from the cell, and GlcN-Ins, used for resynthesis of MSH. The phenotypes of MSH-deficient mutants indicate the occurrence of one or more MSH-dependent S-transferases, peroxidases, and mycoredoxins, which are important targets for future studies. Current evidence suggests that several MSH biosynthetic and metabolic enzymes are potential targets for drugs against tuberculosis. The functions of MSH in antibiotic-producing streptomycetes and in bioremediation are areas for future study.

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Rv2131c gene product: An unconventional enzyme that is both inositol monophosphatase and fructose-1,6-bisphosphatase

Cited by 22 publications

References 29 publications

Biochemistry of the Initial Steps of Mycothiol Biosynthesis

Biochemistry of the Initial Steps of Mycothiol Biosynthesis

Functional identification of sll1383 from Synechocystis sp PCC 6803 as L-myo-inositol 1-phosphate phosphatase (EC 3.1.3.25): molecular cloning, expression and characterization

Biosynthesis and Functions of Mycothiol, the Unique Protective Thiol of Actinobacteria

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