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Literature summary for 3.5.4.39 extracted from

  • Grochowski, L.L.; Xu, H.; Leung, K.; White, R.H.
    Characterization of an Fe(2+)-dependent archaeal-specific GTP cyclohydrolase, MptA, from Methanocaldococcus jannaschii (2007), Biochemistry, 46, 6658-6667.
    View publication on PubMed
Search for more literature for 3.5.4.39

Cloned(Commentary)

Cloned (Comment) Organism
expression in Escherichia coli Methanocaldococcus jannaschii

Protein Variants

Protein Variants Comment Organism
C163S-alkylcysteine when incubated with N-ethylmaleimide, the enzyme loses 67% activity. Iodoacetamide reduces activity by 33% Methanocaldococcus jannaschii
E50D no effect on specific activity of the enzyme Methanocaldococcus jannaschii
H101N mutation does not affect the ability of the enzyme to form dihydro-D-neopterin 2',3'-cyclic phosphate nor does it have a reduced amount of iron Methanocaldococcus jannaschii
H200N/E50D decrease in the specific activity Methanocaldococcus jannaschii
H293N decrease in the specific activity Methanocaldococcus jannaschii
H295N decrease in the specific activity Methanocaldococcus jannaschii
H295N results in a majority of the protein being expressed in an insoluble form Methanocaldococcus jannaschii

Inhibitors

Inhibitors Comment Organism Structure
7-methyl-GTP included along with 2 mM GTP in the incubation mixture. 36% inhibition Methanocaldococcus jannaschii
dGTP included along with 2 mM GTP in the incubation mixture. 28% inhibition Methanocaldococcus jannaschii
fapy-GMP coincubation of MptA with fapyGMP (about 1 mM) and GTP (2 mM) results in a 5-fold reduction in activity Methanocaldococcus jannaschii
GMP included along with 2 mM GTP in the incubation mixture. 43% inhibition Methanocaldococcus jannaschii

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
0.096
-
 GTP pH 7.2, 70°C Methanocaldococcus jannaschii

Metals/Ions

Metals/Ions Comment Organism Structure
Fe2+ required. Mutation of conserved histidine residues H200N, H293N, and H295N, expected to be involved in Fe2+ binding, results in reduced enzymatic activity but no reduction in the amount of bound iron Methanocaldococcus jannaschii
Zn2+ 0.5:1 molar ratio of zinc to enzyme monomer. The zinc content of the mutants H200N and H293N is similar to that of the wild type. Mutant H101N shows an increased amount of zinc (1:1 molar ratio of zinc to monomer) Methanocaldococcus jannaschii

Molecular Weight [Da]

Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
36300
-
 2 * 36300, SDS-PAGE Methanocaldococcus jannaschii
37000
-
 2 * 37000, SDS-PAGE Methanocaldococcus jannaschii
84000
-
 gel filration Methanocaldococcus jannaschii

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
GTP + H2O Methanocaldococcus jannaschii the enzyme is involved in methanopterin biosynthesis in methanogenic archaea 7,8-dihydroneopterin 2',3'-cyclic phosphate + formate + diphosphate
-
 ?

Organism

Organism UniProt Comment Textmining
Methanocaldococcus jannaschii Q58185
-
-

Oxidation Stability

Oxidation Stability Organism
the enzyme readily loses activity upon exposure to air. MptA loses all activity within 4 days at -20°C. This activity can be restored by adding specific divalent metal ions to the oxygen-inactivated enzyme under anaerobic conditions in the presence of dithiothreitol. Only Fe2+ is capable of restoring activity at the physiologically relevant concentrations of 0.020 mM. Higher concentrations of Mn2+ (0.2 mM) are able to restore activity to 24% of that seen with the Fe2+. At very high concentrations (2 mM) Mn2+ is able to restore MptA activity to a higher level than Fe2+. The Mn2+ enzyme is not inactivated by exposure to oxygen. The addition of reducing agents to the assay mixture is able to partially restore activity in oxygen inactivated MptA Methanocaldococcus jannaschii

Purification (Commentary)

Purification (Comment) Organism
-
 Methanocaldococcus jannaschii

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
beta,gamma-methylene-GTP + H2O hydrolyzed at 10% of the specific activity compared to GTP Methanocaldococcus jannaschii ?
-
 ?
GDP + H2O hydrolyzed at about 45% of the specific activity compared to GTP Methanocaldococcus jannaschii ?
-
 ?
GTP + H2O
-
 Methanocaldococcus jannaschii 7,8-dihydroneopterin 2',3'-cyclic phosphate + formate + diphosphate
-
 ?
GTP + H2O the enzyme is involved in methanopterin biosynthesis in methanogenic archaea Methanocaldococcus jannaschii 7,8-dihydroneopterin 2',3'-cyclic phosphate + formate + diphosphate
-
 ?
GTP-gamma-S + H2O hydrolyzed at 130% of the specific activity compared to GTP Methanocaldococcus jannaschii ?
-
 ?
additional information no activity with: dGTP, GMP, 7-methyl-GTP, ATP, fapy-GMP or ITP Methanocaldococcus jannaschii ?
-
 ?

Subunits

Subunits Comment Organism
dimer 2 * 37000, SDS-PAGE Methanocaldococcus jannaschii
dimer 2 * 36300, SDS-PAGE Methanocaldococcus jannaschii

Synonyms

Synonyms Comment Organism
GTP cyclohydrolase MptA
-
 Methanocaldococcus jannaschii
MptA
-
 Methanocaldococcus jannaschii

Temperature Optimum [°C]

Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
70
-
 assay at Methanocaldococcus jannaschii

Temperature Stability [°C]

Temperature Stability Minimum [°C] Temperature Stability Maximum [°C] Comment Organism
80
-
 10 min, 27% loss of activity Methanocaldococcus jannaschii
90
-
 10 min, 60% loss of activity Methanocaldococcus jannaschii
100
-
 10 min, 89% loss of activity Methanocaldococcus jannaschii

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
6.5
-
-
 Methanocaldococcus jannaschii
7.2
-
 assay at Methanocaldococcus jannaschii

pH Range

pH Minimum pH Maximum Comment Organism
6 7.5 pH 6.0: 55% of maximal activity, pH 7.5: about 40% of maximal activity Methanocaldococcus jannaschii