Publications

• Purification and characterization of a novel methyltransferase responsible for biosynthesis of halomethanes and methanethiol in Brassica oleracea.

  Attieh J.M., Hanson A.D., Saini H.S.

  A novel S-adenosyl-L-methionine:halide/bisulfide methyltransferase (EC 2.1.1.-) was purified approximately 1000-fold to apparent homogeneity from leaves of Brassica oleracea. The enzyme catalyzed the S-adenosyl-L-methionine-dependent methylation of the halides iodide, bromide, and chloride to mono ... >> More

  A novel S-adenosyl-L-methionine:halide/bisulfide methyltransferase (EC 2.1.1.-) was purified approximately 1000-fold to apparent homogeneity from leaves of Brassica oleracea. The enzyme catalyzed the S-adenosyl-L-methionine-dependent methylation of the halides iodide, bromide, and chloride to monohalomethanes and of bisulfide to methanethiol. The dual function of the enzyme was demonstrated through co-purification of the halide- and bisulfide-methylating activities in the same ratio and by studies of competition between the alternative substrates iodide and bisulfide. The purification procedure included gel filtration, anion exchange chromatography, and affinity chromatography on adenosine-agarose. Elution of the protein from a chromatofocusing column indicated a pI value of 4.8. The pH optimum of halide methylation (5.5-7.0) was different from that of bisulfide methylation (7.0-8.0). The molecular mass values for the native and denatured protein were 29.5 and 28 kDa, respectively, suggesting that the active enzyme is a monomer. The enzyme had the highest specificity constant for iodide and the next highest for bisulfide. Substrate interaction kinetics and product inhibition patterns were consistent with an Ordered Bi Bi mechanism. << Less

  J Biol Chem 270:9250-9257(1995) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Expression of Batis maritima methyl chloride transferase in Escherichia coli.

  Ni X., Hager L.P.

  Methyl chloride transferase, a novel enzyme found in several fungi, marine algae, and halophytic plants, is a biological catalyst responsible for the production of atmospheric methyl chloride. A previous paper reports the purification of this methylase from Batis maritima and the isolation of a cD ... >> More

  Methyl chloride transferase, a novel enzyme found in several fungi, marine algae, and halophytic plants, is a biological catalyst responsible for the production of atmospheric methyl chloride. A previous paper reports the purification of this methylase from Batis maritima and the isolation of a cDNA clone of the gene for this enzyme. In this paper, we describe the isolation of a genomic clone of the methylase gene and the expression of recombinant methyl chloride transferase in Escherichia coli and compare the kinetic behavior of the wild-type and recombinant enzyme. The recombinant enzyme is active and promotes the production of methyl chloride by E. coli under in vivo conditions. The kinetic data indicate that the recombinant and wild-type enzymes have similar halide (Cl-, Br-, and I-)-binding capacities. Both the recombinant and wild-type enzymes were found to function well in high NaCl concentrations. This high salt tolerance resembles the activity of halobacterial enzymes rather than halophytic plant enzymes. These findings support the hypothesis that this enzyme functions in the control and regulation of the internal concentration of chloride ions in halophytic plant cells. << Less

  Proc Natl Acad Sci U S A 96:3611-3615(1999) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Purification and characterization of a monohalomethane-producing enzyme S-adenosyl-L-methionine: halide ion methyltransferase from a marine microalga, Pavlova pinguis.

  Ohsawa N., Tsujita M., Morikawa S., Itoh N.

  A monohalomethane-producing enzyme, S-adenosyl-L-methionine-dependent halide ion methyltransferase (EC 2.1.1.-) was purified from the marine microalga Pavlova pinguis by two anion exchange, hydroxyapatite and gel filtration chromatographies. The methyltransferase was a monomeric molecule having a ... >> More

  A monohalomethane-producing enzyme, S-adenosyl-L-methionine-dependent halide ion methyltransferase (EC 2.1.1.-) was purified from the marine microalga Pavlova pinguis by two anion exchange, hydroxyapatite and gel filtration chromatographies. The methyltransferase was a monomeric molecule having a molecular weight of 29,000. The enzyme had an isoelectric point at 5.3, and was optimally active at pH 8.0. The Km for iodide and SAM were 12 mM and 12 microM, respectively, which were measured using a partially purified enzyme. Various metal ions had no significant effect on methyl iodide production, suggesting that the enzyme does not require metal ions. The enzyme reaction strictly depended on SAM as a methyl donor, and the enzyme catalyzed methylation of the I-, Br-, and Cl-to corresponding monohalomethanes and of bisulfide to methyl mercaptan. << Less

  Biosci Biotechnol Biochem 65:2397-2404(2001) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Biochemical characterization of chloromethane emission from the wood-rotting fungus phellinus pomaceus.

  Saxena D., Aouad S., Attieh J., Saini H.S.

  Many wood-rotting fungi, including Phellinus pomaceus, produce chloromethane (CH3Cl). P. pomaceus can be cultured in undisturbed glucose mycological peptone liquid medium to produce high amounts of CH3Cl. The biosynthesis of CH3Cl is catalyzed by a methyl chloride transferase (MCT), which appears ... >> More

  Many wood-rotting fungi, including Phellinus pomaceus, produce chloromethane (CH3Cl). P. pomaceus can be cultured in undisturbed glucose mycological peptone liquid medium to produce high amounts of CH3Cl. The biosynthesis of CH3Cl is catalyzed by a methyl chloride transferase (MCT), which appears to be membrane bound. The enzyme is labile upon removal from its natural location and upon storage at low temperature in its bound state. Various detergents failed to solubilize the enzyme in active form, and hence it was characterized by using a membrane fraction. The enzyme had a sharp pH optimum between 7 and 7.2. Its apparent Km for Cl- (ca. 300 mM) was much higher than that for I-(250 &mgr;M) or Br-(11 mM). A comparison of these Km values to the relative in vivo methylation rates for different halides suggests that the real Km for Cl-may be much lower, but the calculated value is high because the CH3Cl produced is used immediately in a coupled reaction. Among various methyl donors tested, S-adenosyl-L-methionine (SAM) was the only one that supported significant methylation by MCT. The reaction was inhibited by S-adenosyl-L-homocysteine, an inhibitor of SAM-dependent methylation, suggesting that SAM is the natural methyl donor. These findings advance our comprehension of a poorly understood metabolic sector at the origin of biogenic emissions of halomethanes, which play an important role in atmospheric chemistry. << Less

  Appl Environ Microbiol 64:2831-2835(1998) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Involvement of S-adenosylmethionine-dependent halide/thiol methyltransferase (HTMT) in methyl halide emissions from agricultural plants: isolation and characterization of an HTMT-coding gene from Raphanus sativus (daikon radish).

  Itoh N., Toda H., Matsuda M., Negishi T., Taniguchi T., Ohsawa N.

  <h4>Background</h4>Biogenic emissions of methyl halides (CH3Cl, CH3Br and CH3I) are the major source of these compounds in the atmosphere; however, there are few reports about the halide profiles and strengths of these emissions. Halide ion methyltransferase (HMT) and halide/thiol methyltransferas ... >> More

  <h4>Background</h4>Biogenic emissions of methyl halides (CH3Cl, CH3Br and CH3I) are the major source of these compounds in the atmosphere; however, there are few reports about the halide profiles and strengths of these emissions. Halide ion methyltransferase (HMT) and halide/thiol methyltransferase (HTMT) enzymes concerning these emissions have been purified and characterized from several organisms including marine algae, fungi, and higher plants; however, the correlation between emission profiles of methyl halides and the enzymatic properties of HMT/HTMT, and their role in vivo remains unclear.<h4>Results</h4>Thirty-five higher plant species were screened, and high CH3I emissions and HMT/HTMT activities were found in higher plants belonging to the Poaceae family, including wheat (Triticum aestivum L.) and paddy rice (Oryza sativa L.), as well as the Brassicaceae family, including daikon radish (Raphanus sativus). The in vivo emission of CH3I clearly correlated with HMT/HTMT activity. The emission of CH3I from the sprouting leaves of R. sativus, T. aestivum and O. sativa grown hydroponically increased with increasing concentrations of supplied iodide. A gene encoding an S-adenosylmethionine halide/thiol methyltransferase (HTMT) was cloned from R. sativus and expressed in Escherichia coli as a soluble protein. The recombinant R. sativus HTMT (RsHTMT) was revealed to possess high specificity for iodide (I-), bisulfide ([SH]-), and thiocyanate ([SCN]-) ions.<h4>Conclusion</h4>The present findings suggest that HMT/HTMT activity is present in several families of higher plants including Poaceae and Brassicaceae, and is involved in the formation of methyl halides. Moreover, it was found that the emission of methyl iodide from plants was affected by the iodide concentration in the cultures. The recombinant RsHTMT demonstrated enzymatic properties similar to those of Brassica oleracea HTMT, especially in terms of its high specificity for iodide, bisulfide, and thiocyanate ions. A survey of biogenic emissions of methyl halides strongly suggests that the HTM/HTMT reaction is the key to understanding the biogenesis of methyl halides and methylated sulfur compounds in nature. << Less

  BMC Plant Biol 9:116-116(2009) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.