Methylthioadenosine

Schlenk, F.

doi:10.1002/9780470122990.ch4

Cited by 27 publications

(18 citation statements)

References 265 publications

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“…This result is consistent with the fact that, in animals, MTA recycling does not involve hydrolysis of MTA to MTR by MTA nucleosidase and subsequent phosphorylation of MTR by MTR kinase as in plants and in bacteria. Instead, MTA is phosphorylated and cleaved to methylthio-Rib-1-P and adenine in one step by the enzyme 5#-deoxy-5#-methylthioadenosine phosphorylase (Schlenk, 1983;Thomas and Surdin-Kerjan, 1997). Our homology search did not reveal a yeast MTK homolog and thus confirmed previously published biochemical data indicating that yeast conforms to the animal-type Met recycling pathway with phosphorylytic cleavage of MTA (Marchitto and Ferro, 1985).…”

Section: Mtr Kinases Are Encoded By Unique Genes In Most Plantsmentioning

confidence: 99%

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Functional Analysis of Methylthioribose Kinase Genes in Plants

et al. 2004

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Through a biochemical and a genetic approach, we have identified several plant genes encoding methylthioribose (MTR) kinase, an enzyme involved in recycling of methionine through the methylthioadenosine (MTA) cycle. OsMTK1, an MTR kinase from rice (Oryza sativa), is 48.6 kD in size and shows cooperative kinetics with a V max of 4.9 pmol/min and a K 0.5 of 16.8 mM. MTR kinase genes are the first genes to be identified from the MTA cycle in plants. Insertional mutagenesis of the unique AtMTK gene in Arabidopsis (Arabidopsis thaliana) resulted in an inability of plants to grow on MTA as a supplemental sulfur source. MTK knock-out plants were not impaired in growth under standard conditions, indicating that the MTA cycle is a nonessential metabolic pathway in Arabidopsis when sulfur levels are replete. In rice, OsMTK genes were strongly upregulated in shoots and roots when plants were exposed to sulfur starvation. Gene expression was largely unaffected by lack of nitrogen or iron in the nutrient solution, indicating that OsMTK regulation was linked specifically to sulfur metabolism.

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Section: Mtr Kinases Are Encoded By Unique Genes In Most Plantsmentioning

confidence: 99%

“…MTR kinase catalyzes the subsequent phosphorylation of the C-1 hydroxyl group of the Rib moiety of MTR to yield 5-methylthio-Rib-1-P. In animals, MTA phosphorylase carries out both functions in a single ATP-independent step (Schlenk, 1983). Hence, MTR kinase exists in prokaryotes and plant species but not in animals.…”

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Functional Analysis of Methylthioribose Kinase Genes in Plants

et al. 2004

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“…The first committed intermediate in the MSP, methylthioadenosine (MTA), is formed from S-adenosylmethionine (SAM, AdoMet) as a biproduct of polyamine biosynthesis. MTA is a potent inhibitor of polyamine biosynthesis and transmethylation reactions (1). In turn, polyamines are important in the regulation of the cell cycle, being required for cell growth and proliferation.…”

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Characterization of Metal Binding in the Active Sites of Acireductone Dioxygenase Isoforms from Klebsiella ATCC 8724

Chai

Dang

et al. 2008

Biochemistry

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The two acireductone dioxygenase (ARD) isozymes from the methionine salvage pathway of Klebsiella ATCC 8724 present an unusual case in which two enzymes with different structures and distinct activities towards their common substrates (1,2-dihydroxy-3-oxo-5-(methylthio)pent-1-ene and dioxygen) are derived from the same polypeptide chain. Structural and functional differences between the two isozymes are determined by the type of M +2 metal ion bound in the active site. The Ni +2 -bound NiARD catalyzes an off-pathway shunt from the methionine salvage pathway leading to the production of formate, methylthiopropionate and carbon monoxide, while the Fe +2 -bound FeARD' catalyzes the on-pathway formation of methionine precursor 2-keto-4-methylthiobutyrate and formate. Four potential protein-based metal ligands were identified by sequence homology and structural considerations. Based on the results of site-directed mutagenesis experiments, X-ray absorption spectroscopy (XAS) and isothermal calorimetry measurements, it is concluded that the same four residues, His 96, His 98, Glu 102 and His 140, provide the protein-based ligands for the metal in both the Ni-and Fe-containing forms of the enzyme, and subtle differences in the local backbone conformations trigger the observed structural and functional differences between the FeARD' and NiARD isozymes. Furthermore, both forms of the enzyme bind their respective metals with pseudo-octahedral geometry, and both may lose a His ligand upon binding of substrate under anaerobic conditions. However, mutations at two conserved non-ligand acidic residues, Glu 95 and Glu 100, result in low metal contents for the mutant proteins as isolated, suggesting that some of the conserved charged residues may aid in transfer of metal from in vivo sources or prevent the loss of metal to stronger chelators. The Glu 100 mutant reconstitutes readily but has low activity. Mutation of Asp 101 results in an active enzyme that incorporates metal in vivo but shows evidence of mixed forms.* To whom correspondence should be addressed: pochapsk@brandeis.edu, phone 781−736−2559, fax 781−736−2516. e Current address: Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, 70 Ship Street, GE3, Providence, RI, 02912 f Current address: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Dr., Room 1007, Indianapolis IN 46202 g This work was supported in part by USPHS grant (R01-GM067786 TCP). Acknowledgment is made to the donors of The American Chemical Society Petroleum Research Fund for partial support (MJM). Trainee funding (SCC) was provided by the NIH-Chemistry Biology Interface Program, T32-GM08515. XAS data collection at the National Synchrotron Light Source at Brookhaven National Laboratory was supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences. Beamline X9B at NSLS is supported in part by the NIH.Supporting information available Fits for resting state and ES...

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“…These enzymes are thought to be important in elimination of MTA and SAH, toxic by-products of metabolic pathways, in the salvage of purines and/or methionine, and in the production of a precursor of the quorum-sensing molecule, autoinducer 2 (AI-2) (2,6,9,42,45,53). Unlike Bgp, Pfs in most bacteria is localized to the bacterial cytoplasm.…”

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confidence: 99%

“…Both purified His-tagged Bgp and Pfs-1 showed nucleosidase activity when assayed as previously described (15,28) (45). The specific activities for Bgp and Pfs-1 were calculated to be 13 mol/min/mg and 7 mol/min/mg, respectively (Fig.…”

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confidence: 99%