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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

Gene-Reaction Schematic


GO Terms:
Cellular Component:
GO:0005829 - cytosol [Emes73]

Enzymatic reaction of: phenylalanine transaminase

Inferred from experiment

EC Number: 2.6.1.58

L-phenylalanine + pyruvate ⇄ 2-oxo-3-phenylpropanoate + L-alanine

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction in which it was curated.

This reaction is reversible.


Enzymatic reaction of: histidine-pyruvate aminotransferase

Inferred from experiment

EC Number: 2.6.1.58

L-histidine + pyruvate ⇄ imidazole-pyruvate + L-alanine

The direction shown, i.e. which substrates are on the left and right sides, 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: L-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 Pathway Tools version 19.5 (software by SRI International) on Sat Feb 13, 2016, biocyc12.