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Literature summary extracted from

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

Activating Compound

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

General Stability

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

Inhibitors

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

KM Value [mM]

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

Metals/Ions

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

Molecular Weight [Da]

EC Number Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
4.2.1.33 90000
-
 sucrose density gradient centrifugation, gel filtration Neurospora sp.
4.2.1.33 90000
-
 sucrose density gradient centrifugation, gel filtration Salmonella sp.

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
4.2.1.33 2-isopropylmaleate + H2O Neurospora sp. high activities in leu-1 mutants which have accumulated great amounts of inducer ?
-
 ?
4.2.1.33 2-isopropylmaleate + H2O Neurospora sp. second of three reactions of leucine biosynthesis ?
-
 ?
4.2.1.33 2-isopropylmaleate + H2O Salmonella sp. second of three reactions of leucine biosynthesis ?
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
4.2.1.33 Neurospora sp.
-
-
-
4.2.1.33 Salmonella sp.
-
-
-

Purification (Commentary)

EC Number Purification (Comment) Organism
4.2.1.33
-
 Neurospora sp.

Reaction

EC Number Reaction Comment Organism Reaction ID
4.2.1.33 (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.
a

Specific Activity [micromol/min/mg]

EC Number Specific Activity Minimum [µmol/min/mg] Specific Activity Maximum [µmol/min/mg] Comment Organism
4.2.1.33 12.3
-
-
 Neurospora sp.

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
4.2.1.33 2-isopropylmaleate + H2O
-
 Neurospora sp. 3-isopropylmalate
-
 ?
4.2.1.33 2-isopropylmaleate + H2O
-
 Salmonella sp. 3-isopropylmalate
-
 ?
4.2.1.33 2-isopropylmaleate + H2O high activities in leu-1 mutants which have accumulated great amounts of inducer Neurospora sp. ?
-
 ?
4.2.1.33 2-isopropylmaleate + H2O second of three reactions of leucine biosynthesis Neurospora sp. ?
-
 ?
4.2.1.33 2-isopropylmaleate + H2O second of three reactions of leucine biosynthesis Salmonella sp. ?
-
 ?
4.2.1.33 3-isopropylmalate
-
 Neurospora sp. 2-isopropylmaleate + H2O
-
 ?
4.2.1.33 3-isopropylmalate
-
 Salmonella sp. 2-isopropylmaleate + H2O
-
 ?
4.2.1.33 additional information citrate, aconitate, isocitrate are not substrates Neurospora sp. ?
-
 ?
4.2.1.33 additional information citrate, aconitate, isocitrate are not substrates Salmonella sp. ?
-
 ?

Subunits

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

Temperature Stability [°C]

EC Number Temperature Stability Minimum [°C] Temperature Stability Maximum [°C] Comment Organism
4.2.1.33 45
-
 95% loss of activity after 10 min Neurospora sp.
4.2.1.33 45
-
 95% loss of activity after 10 min Salmonella sp.

pH Optimum

EC Number pH Optimum Minimum pH Optimum Maximum Comment Organism
4.2.1.33 7 8
-
 Neurospora sp.

pH Range

EC Number pH Minimum pH Maximum Comment Organism
4.2.1.33 6 8 at pH 6.0, 20% of optimum activity, activity varies only about 20% between pH 7.0 and 8.0 Neurospora sp.
4.2.1.33 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

EC Number pH Stability pH Stability Maximum Comment Organism
4.2.1.33 6 6.5 unstable at pH 7.0 Neurospora sp.