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Literature summary for 4.2.1.33 extracted from

  • Gross, S.R.
    Isopropylmalate isomerase (Neurospora) (1970), Methods Enzymol., 17A, 786-790.
No PubMed abstract available

Activating Compound

Activating Compound Comment Organism Structure
additional information no requirement Neurospora sp.
additional information no requirement Salmonella sp.

General Stability

General Stability Organism
loss of activity after repeated freezing and thawing Neurospora sp.
loss of activity after repeated freezing and thawing Salmonella sp.
substrate stabilizes Neurospora sp.
substrate stabilizes Salmonella sp.
unstable in phosphate buffer at pH 7.0, 10% loss of activity per h at 0°C Neurospora sp.
unstable in phosphate buffer at pH 7.0, 10% loss of activity per h at 0°C Salmonella sp.

Inhibitors

Inhibitors Comment Organism Structure
Cu2+ complete inhibition at 10 mM Neurospora sp.
cysteine complete inhibition at 0.004-0.02 mM Neurospora sp.
dimethylmesaconate
-
Neurospora sp.
Hg2+ complete inhibition at 10 mM Neurospora sp.
isopropylmalate
-
Neurospora sp.
isopropylmalate
-
Salmonella sp.
N-ethylmaleimide 65% inhibition after preincubation in 1 mM Neurospora sp.
N-ethylmaleimide
-
Salmonella sp.

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
additional information Ks for standard substrates Neurospora sp.

Metals/Ions

Metals/Ions Comment Organism Structure
additional information no requirement Neurospora sp.
additional information no requirement Salmonella sp.

Molecular Weight [Da]

Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
90000
-
sucrose density gradient centrifugation, gel filtration Neurospora sp.
90000
-
sucrose density gradient centrifugation, gel filtration Salmonella sp.

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
2-isopropylmaleate + H2O Neurospora sp. high activities in leu-1 mutants which have accumulated great amounts of inducer ?
-
?
2-isopropylmaleate + H2O Neurospora sp. second of three reactions of leucine biosynthesis ?
-
?
2-isopropylmaleate + H2O Salmonella sp. second of three reactions of leucine biosynthesis ?
-
?

Organism

Organism UniProt Comment Textmining
Neurospora sp.
-
-
-
Salmonella sp.
-
-
-

Purification (Commentary)

Purification (Comment) Organism
-
Neurospora sp.

Reaction

Reaction Comment Organism Reaction ID
(2R,3S)-3-isopropylmalate = 2-isopropylmaleate + H2O stoichiometry of reaction, enzyme also hydrates 2-isopropylmaleate to 3-hydroxy-4-methyl-3-carboxypentanoate, interconversion between the 2 isomers Neurospora sp.

Specific Activity [micromol/min/mg]

Specific Activity Minimum [µmol/min/mg] Specific Activity Maximum [µmol/min/mg] Comment Organism
12.3
-
-
Neurospora sp.

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2-isopropylmaleate + H2O
-
Neurospora sp. 3-isopropylmalate
-
?
2-isopropylmaleate + H2O
-
Salmonella sp. 3-isopropylmalate
-
?
2-isopropylmaleate + H2O high activities in leu-1 mutants which have accumulated great amounts of inducer Neurospora sp. ?
-
?
2-isopropylmaleate + H2O second of three reactions of leucine biosynthesis Neurospora sp. ?
-
?
2-isopropylmaleate + H2O second of three reactions of leucine biosynthesis Salmonella sp. ?
-
?
3-isopropylmalate
-
Neurospora sp. 2-isopropylmaleate + H2O
-
?
3-isopropylmalate
-
Salmonella sp. 2-isopropylmaleate + H2O
-
?
additional information citrate, aconitate, isocitrate are not substrates Neurospora sp. ?
-
?
additional information citrate, aconitate, isocitrate are not substrates Salmonella sp. ?
-
?

Subunits

Subunits Comment Organism
tetramer trimer or tetramer of 2 different polypeptide subunits Neurospora sp.
trimer trimer or tetramer of 2 different polypeptide subunits Neurospora sp.

Temperature Stability [°C]

Temperature Stability Minimum [°C] Temperature Stability Maximum [°C] Comment Organism
45
-
95% loss of activity after 10 min Neurospora sp.
45
-
95% loss of activity after 10 min Salmonella sp.

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
7 8
-
Neurospora sp.

pH Range

pH Minimum pH Maximum Comment Organism
6 8 at pH 6.0, 20% of optimum activity, activity varies only about 20% between pH 7.0 and 8.0 Neurospora sp.
6 8 at pH 6.0, 20% of optimum activity, activity varies only about 20% between pH 7.0 and 8.0 Salmonella sp.

pH Stability

pH Stability pH Stability Maximum Comment Organism
6 6.5 unstable at pH 7.0 Neurospora sp.