Publications

• S-adenosyl-L-methionine:L-methionine S-methyltransferase from germinating barley. Purification and localization.

  Pimenta M.J., Kaneta T., Larondelle Y., Dohmae N., Kamiya Y.

  S-Adenosyl-L-methionine:L-methionine S-methyltransferase (MMT) catalyzes the synthesis of S-methyl-L-methionine (SMM) from L-methionine and S-adenosyl-L-methionine. SMM content increases during barley (Hordeum vulgare L.) germination. Elucidating the role of this compound is important from both a ... >> More

  S-Adenosyl-L-methionine:L-methionine S-methyltransferase (MMT) catalyzes the synthesis of S-methyl-L-methionine (SMM) from L-methionine and S-adenosyl-L-methionine. SMM content increases during barley (Hordeum vulgare L.) germination. Elucidating the role of this compound is important from both a fundamental and a technological standpoint, because SMM is the precursor of dimethylsulfide, a biogenic source of atmospheric S and an undesired component in beer. We present a simple purification scheme for the MMT from barley consisting of 10% to 25% polyethylene glycol fractionation, anion-exchange chromatography on diethylaminoethyl-Sepharose, and affinity chromatography on adenosine-agarose. A final activity yield of 23% and a 2765-fold purification factor were obtained. After digestion of the protein with protease, the amino acid sequence of a major peptide was determined and used to produce a synthetic peptide. A polyclonal antibody was raised against this synthetic peptide conjugated to activated keyhole limpet hemocyanin. The antibody recognized the 115-kD denatured MMT protein and native MMT. During barley germination, both the specific activity and the amount of MMT protein increased. MMT-specific activity was found to be higher in the root and shoot than in the endosperm. MMT could be localized by an immunohistochemical approach in the shoot, scutellum, and aleurone cells but not in the root or endosperm (including aleurone). << Less

  Plant Physiol. 118:431-438(1998) [PubMed] [EuropePMC]

• Purification and properties of S-adenosyl-L-methionine:L-methionine S-methyltransferase from Wollastonia biflora leaves.

  James F., Nolte K.D., Hanson A.D.

  The plant enzyme S-adenosylmethionine:methionine S-methyltransferase (EC 2.1.1.12, MMT) catalyzes the synthesis of S-methylmethionine. MMT was purified 620-fold to apparent homogeneity from leaves of Wollastonia biflora. The four-step purification included fractionation with polyethylene glycol, a ... >> More

  The plant enzyme S-adenosylmethionine:methionine S-methyltransferase (EC 2.1.1.12, MMT) catalyzes the synthesis of S-methylmethionine. MMT was purified 620-fold to apparent homogeneity from leaves of Wollastonia biflora. The four-step purification included fractionation with polyethylene glycol, affinity chromatography on adenosine-agarose, anion exchange chromatography, and gel filtration. Protein yield was about 180 micrograms/kg of leaves. Estimates of molecular mass from sodium dodecyl sulfate-polyacrylamide gel electrophoresis and native gel filtration chromatography were, respectively, 115 and 450 kDa, suggesting a tetramer of 115-kDa subunits. The 115-kDa subunit was photoaffinity labeled by S-adenosyl[3H]methionine. Antibodies raised against W. biflora MMT recognized a 115-kDa polypeptide in partially purified MMT preparations from leaves of lettuce, cabbage, clover, and maize. The pH optimum of W. biflora MMT was 7.2. Kinetic analysis of substrate interaction and product inhibition patterns indicated an Ordered Bi Bi mechanism, with S-adenosylmethionine the first reactant to bind and S-adenosylhomocysteine the last product to be released. The enzyme catalyzed methylation of selenomethionine and ethionine, but not of S-methylcysteine, homocysteine, cysteine, or peptidylmethionine. Tests with other substrate analogs indicated that a free carboxyl group was required for enzyme activity, and that a free amino group was not. << Less

  J. Biol. Chem. 270:22344-22350(1995) [PubMed] [EuropePMC]

• S-methylmethionine plays a major role in phloem sulfur transport and is synthesized by a novel type of methyltransferase.

  Bourgis F., Roje S., Nuccio M.L., Fisher D.B., Tarczynski M.C., Li C., Herschbach C., Rennenberg H., Pimenta M.J., Shen T.-L., Gage D.A., Hanson A.D.

  All flowering plants produce S-methylmethionine (SMM) from Met and have a separate mechanism to convert SMM back to Met. The functions of SMM and the reasons for its interconversion with Met are not known. In this study, by using the aphid stylet collection method together with mass spectral and r ... >> More

  All flowering plants produce S-methylmethionine (SMM) from Met and have a separate mechanism to convert SMM back to Met. The functions of SMM and the reasons for its interconversion with Met are not known. In this study, by using the aphid stylet collection method together with mass spectral and radiolabeling analyses, we established that l-SMM is a major constituent of the phloem sap moving to wheat ears. The SMM level in the phloem ( approximately 2% of free amino acids) was 1.5-fold that of glutathione, indicating that SMM could contribute approximately half the sulfur needed for grain protein synthesis. Similarly, l-SMM was a prominently labeled product in phloem exudates obtained by EDTA treatment of detached leaves from plants of the Poaceae, Fabaceae, Asteraceae, Brassicaceae, and Cucurbitaceae that were given l-(35)S-Met. cDNA clones for the enzyme that catalyzes SMM synthesis (S-adenosylMet:Met S-methyltransferase; EC 2.1.1.12) were isolated from Wollastonia biflora, maize, and Arabidopsis. The deduced amino acid sequences revealed the expected methyltransferase domain ( approximately 300 residues at the N terminus), plus an 800-residue C-terminal region sharing significant similarity with aminotransferases and other pyridoxal 5'-phosphate-dependent enzymes. These results indicate that SMM has a previously unrecognized but often major role in sulfur transport in flowering plants and that evolution of SMM synthesis in this group involved a gene fusion event. The resulting bipartite enzyme is unlike any other known methyltransferase. << Less

  Plant Cell 11:1485-1498(1999) [PubMed] [EuropePMC]