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discounted EARLY registration ends Dec 31, 2014
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discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
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MetaCyc Enzyme: phenylalanine transaminase / histidine-pyruvate aminotransferase

Species: Rattus norvegicus

Subunit composition of phenylalanine transaminase / histidine-pyruvate aminotransferase = [histidine-pyruvate aminotransferase subunit]

Summary:
Two forms of phenylalanine transaminase / histidine-pyruvate aminotransferase have been isolated from rat liver - a soluble form and a membrane-bound mitochondrial form [Emes73]. Both enzymes had relatively broad specificity, with significant activity towards L-phenylalanine and L-tyrosine, and catalyzed transamination with a number of mono-carboxylic 2-oxo acids. However, unlike the prokaryotic enzyme, the enzymes from rat liver could not use 2-oxoglutarate.

The soluble enzyme, described here, has a lower Km for L-histidine than the particulate mitochondrial enzyme (1.2 mM and 8.3 mM, respectively). A difference in optimal pH was also observed (9.2-9.4 and 8.9-9.1, respectively). While an absolute requirement for pyridoxal 5'-phosphate could not be demonstrated, addition of the cofactor enhanced the reaction by 25-60% [Emes73].

Locations: cytosol

Molecular Weight of Multimer: 150 kD (experimental) [Emes73]

Gene-Reaction Schematic: ?

GO Terms:

Cellular Component: GO:0005829 - cytosol [Emes73]


Enzymatic reaction of: phenylalanine transaminase

EC Number: 2.6.1.58

L-phenylalanine + pyruvate <=> 2-oxo-3-phenylpropanoate + L-alanine

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

This reaction is reversible.


Enzymatic reaction of: histidine-pyruvate aminotransferase

EC Number: 2.6.1.58

L-histidine + pyruvate <=> imidazole-pyruvate + L-alanine

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

This reaction is reversible.

Alternative Substrates for pyruvate: glyoxylate [Emes73 ] , 4-methyl-2-oxopentanoate [Emes73 ] , 2-oxohexanoate [Emes73 ] , 2-oxobutanoate [Emes73 ]

Alternative Substrates for L-histidine: L-tyrosine [Emes73 ] , L-phenylalanine [Emes73 ]

In Pathways: histidine degradation V

Activators (Allosteric): pyridoxal 5'-phosphate [Emes73]

Kinetic Parameters:

Substrate
Km (μM)
Citations
L-histidine
1200.0
[Emes73]

pH(opt): 9.2-9.4 [Emes73]


References

Emes73: Emes AV, Hassall H (1973). "The degradation of L-histidine in the rat. The formation of imidazolylpyruvate, imidazolyl-lactate and imidazolylpropionate." Biochem J 136(3);649-58. PMID: 4360716


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Thu Dec 18, 2014, biocyc11.