; The enzyme is specific for xanthosine, as XMP and xanthine cannot act as substrates [2,4]. The enzyme does not have N1- or N3- methylation activity. This is the first methylation step in the production of caffeine.
The enzyme is specific for xanthosine, as XMP and xanthine cannot act as substrates [2,4]. The enzyme does not have N1- or N3- methylation activity [2]. This is the first methylation step in the production of caffeine.
methylation of xanthosine by 7-methylxanthosine synthase is the most plausible rate-limiting step of caffeine biosynthesis, the supply of non-methylated purine precursors or availability of S-adenosyl-L-methionine are not the principal controlling factors of caffeine biosynthesis
the enzyme is part of a caffeine biosynthetic pathway which includes a recycling of adenosine released from S-adenosyl-L-methionine in form of xanthosine monophosphate, overview
first step in caffeine biosynthesis pathway from xanthosine, reduction of the second enzyme of the pathway, 7-methylxanthine methyltransferase, EC 2.1.1.159, leads to reduced XMT1 expression
first step in caffeine biosynthesis pathway from xanthosine, reduction of the second enzyme of the pathway, 7-methylxanthine methyltransferase, EC 2.1.1.159, leads to reduced XMT1 expression
the enzyme is part of a caffeine biosynthetic pathway which includes a recycling of adenosine released from S-adenosyl-L-methionine in form of xanthosine monophosphate, overview
first step in caffeine biosynthesis pathway from xanthosine, reduction of the second enzyme of the pathway, 7-methylxanthine methyltransferase, EC 2.1.1.159, leads to reduced XMT1 expression
first step in caffeine biosynthesis pathway from xanthosine, reduction of the second enzyme of the pathway, 7-methylxanthine methyltransferase, EC 2.1.1.159, leads to reduced XMT1 expression
bimolecular fluorescence complementation. Enzymes xanthosine methyltransferase, 7-methylxanthine methyltransferase, and 3,7-dimethylxanthine methyltransferase each form a homo-dimer in cytosol. In addition, each enzyme also forms a hetero-dimer with each of the other two enzymes in cytosol
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
purified recombinant wild-type and selenomethionine-labeled XMT, 23-28% PEG 3350, 0.2 M LiCl, 0.1 M Tris-HCl, pH 8.5-8.7, 2 mM DTT, 1 mM S-adenosyl-L-cysteine, and 1 mM xanthosine, 1-3 days, 20°C, X-ray diffraction structure determination and analysis at 2.8-3.0 A resolution
purified recombinant wild-type and selenomethionine-labeled XMT, 23-28% PEG 3350, 0.2 M LiCl, 0.1 M Tris-HCl, pH 8.5-8.7, 2 mM DTT, 2 mM S-adenosyl-L-cysteine, and 2 mM xanthosine, 1-3 days, 20°C, plate-like crystals, X-ray diffraction structure determination and analysis at 2.2 A resolution
recombinant His-tagged XMT1 from Escherichia coli strain BL21(DE3) to homogeneity by nickel affinity chromatography, cleavage of the His-tag with tobacco etch virus, TEV, protease, followed by gel filtration
isozyme XMT1, DNA and amino acid sequence determination and analysis, phylogenetic analysis, expression of the GST-tagged enzyme in Escherichia coli Bl21(DE3)
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
A23S
Coffea sp.
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site-directed mutagenesis, the mutant exhibits no 3-N methylation activity like the wild-type, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits no 3-N methylation activity like the wild-type, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits no 3-N methylation activity like the wild-type, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows 60% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits no 3-N methylation activity like the wild-type, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits no 3-N methylation activity like the wild-type, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits no 3-N methylation activity like the wild-type, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits no 3-N methylation activity like the wild-type, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows over 80% of wild-type 7-methylation activity
site-directed mutagenesis, the mutant exhibits 3-N methylation activity in contrast to the wild-type enzyme, the mutant shows over 80% of wild-type 7-methylation activity
transgenic Nicotiana tabacum plant leaves expressing all three enzymes required for the biosynthesis of caffeine are no longer eaten by the tobacco cutworm caterpillars, Spodoptera litura, overview
construction of several enzyme mutants, overview. The mutants of CmXRS1, that have 3-N methylation activity and produce caffeine from paraxanthine as a substrate, need to have replacement of the glutamine residue by histidine at position 161 in the CmXRS1 sequence, i.e. a Q161H mutation, overview
Mizuno, K.; Kato, M.; Irino, F.; Yoneyama, N.; Fujimura, T.; Ashihara, H.
The first committed step reaction of caffeine biosynthesis: 7-methylxanthosine synthase is closely homologous to caffeine synthases in coffee (Coffea arabica L.)
Application of RNAi to confirm theobromine as the major intermediate for caffeine biosynthesis in coffee plants with potential for construction of decaffeinated varieties
Uefuji, H.; Ogita, S.; Yamaguchi, Y.; Koizumi, N.; Sano, H.
Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants