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MetaCyc Enzyme: tryptophan aminotransferase

Gene: TAA1 Accession Number: AT1G70560 (MetaCyc)

Synonyms: SAV3, WEI8

Species: Arabidopsis thaliana col

Summary:
The TAA1 protein is involved in the formation of indole-3-pyruvate, a precursor to indole-3-acetate (IAA), a biologically important auxin that acts as a phytohormone in many plant species [Tao08, Stepanova08, Woodward05]. In vitro assays reveal that this pyridoxal 5'-phosphate (PLP)-dependent aminotransferase can act on a number of different L-amino acids, including L-phenylalaine, L-tyrosine, L-leucine, L-alanine, L-methionine, and L-glutamine using either pyruvate or 2-oxoglutarate as a cosubstrate [Tao08]. However, enzymatic assays, in silico docking experiments, and mutant phenotypic analyses all suggest that L-tryptophan is the in vivo substrate for this enzyme [Tao08, Stepanova08]. TAA1 has a Km of 0.29 mM and a Vmax of 12.9 μM/min when tested with L-tryptophan and pyruvate [Tao08]. It is unclear whether pyruvate or 2-oxoglutarate is the more biologically relevant cosubstrate for this enzyme.

The gene encoding this protein was identified in screens for shade avoidance mutants [Tao08] and mutants with a weak ethylene insensitivity [Stepanova08] suggesting that the auxin synthesized through a TAA1-mediated pathway is particularly important for the responses to specific environmental and hormonal stimuli. In addition, normal developmental processes, such as embryogenesis, that require proper auxin levels, are disrupted when TAA1 and one or more of its closely related family members (i.e. TAR1 and TAR2) are knocked-out in Arabidopsis plants [Stepanova08].

This enzyme activity appears to be widely distributed in the plant kingdom, based on the ability of enzymatic extracts from 30 different species distributed among 16 families, to catalyze the formation of IPA in a transaminase reaction [Truelsen72]. Three species of algae also have this activity [Truelsen72].

Locations: cytoplasm

Molecular Weight of Polypeptide: 44.801 kD (from nucleotide sequence)

Unification Links: Entrez-gene:843393 , PhylomeDB:Q9S7N2 , Pride:Q9S7N2 , Protein Model Portal:Q9S7N2 , SMR:Q9S7N2 , String:3702.AT1G70560.1-P , UniProt:Q9S7N2

Relationship Links: InterPro:IN-FAMILY:IPR006947 , InterPro:IN-FAMILY:IPR006948 , InterPro:IN-FAMILY:IPR015421 , InterPro:IN-FAMILY:IPR015422 , InterPro:IN-FAMILY:IPR015424 , PDB:Structure:3BWN , PDB:Structure:3BWO , Pfam:IN-FAMILY:PF04864

Gene-Reaction Schematic: ?

GO Terms:

Cellular Component: GO:0005737 - cytoplasm [Tao08]

Credits:
Created 02-Apr-2009 by Dreher KA , TAIR


Enzymatic reaction of: L-phenylalanine:2-oxoglutarate aminotransferase (tryptophan aminotransferase)

Synonyms: L-phenylalanine:2-oxoglutarate transaminase, L-phenylalanine:α-ketoglutarate aminotransferase, L-phenylalanine:α-ketoglutarate transaminase

2-oxo-3-phenylpropanoate + L-glutamate <=> L-phenylalanine + 2-oxoglutarate

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: L-tyrosine:pyruvate aminotransferase (tryptophan aminotransferase)

Synonyms: L-tyrosine:pyruvate transaminase

EC Number: 2.6.1.58

L-tyrosine + pyruvate <=> 4-hydroxyphenylpyruvate + 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.

Kinetic Parameters:

Substrate
Km (μM)
Citations
L-tyrosine
4960.0
[Tao08]


Enzymatic reaction of: L-alanine:2-oxoglutarate aminotransferase (tryptophan aminotransferase)

Synonyms: L-alanine:2-oxoglutarate transaminase, L-alanine:α-ketoglutarate transaminase, L-alanine:α-ketoglutarate aminotransferase

EC Number: 2.6.1.2

2-oxoglutarate + L-alanine <=> L-glutamate + pyruvate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

This reaction is reversible.


Enzymatic reaction of: L-leucine:2-oxoglutarate aminotransferase (tryptophan aminotransferase)

Synonyms: L-leucine:α-ketoglutarate aminotransferase, L-leucine:2-oxoglutarate transaminase, L-leucine:α-ketoglutarate transaminase

EC Number: 2.6.1.6/2.6.1.42

L-leucine + 2-oxoglutarate <=> L-glutamate + 4-methyl-2-oxopentanoate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

This reaction is reversible.


Enzymatic reaction of: L-tyrosine:2-oxoglutarate aminotransferase (tryptophan aminotransferase)

Synonyms: L-tyrosine:α-ketoglutarate aminotransferase, L-tyrosine:2-oxoglutarate transaminase, L-tyrosine:α-ketoglutarate transaminase

L-tyrosine + 2-oxoglutarate <=> 4-hydroxyphenylpyruvate + L-glutamate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

This reaction is reversible.

In Pathways: superpathway of plastoquinol biosynthesis , 4-hydroxyphenylpyruvate biosynthesis


Enzymatic reaction of: L-phenylalanine:pyruvate aminotransferase (tryptophan aminotransferase)

Synonyms: L-phenylalanine:pyruvate 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.

Kinetic Parameters:

Substrate
Km (μM)
Citations
L-phenylalanine
9080.0
[Tao08]


Enzymatic reaction of: L-tryptophan:pyruvate aminotransferase (tryptophan aminotransferase)

Synonyms: L-tryptophan:pyruvate transaminase

EC Number: 2.6.1.99

L-tryptophan + pyruvate <=> L-alanine + indole-3-pyruvate

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.

In Pathways: indole-3-acetate biosynthesis I , indole-3-acetate biosynthesis II

Summary:
Enzymatic assays, in silico docking experiments, and mutant phenotypic analyses all suggest that L-tryptophan is the in vivo substrate for this enzyme [Tao08, Stepanova08]. TAA1 has a Km of 0.29 mM and a Vmax of 12.9 μM/min when tested with L-tryptophan and pyruvate [Tao08]. It is unclear whether pyruvate or 2-oxoglutarate is the more biologically relevant cosubstrate for this enzyme.

Cofactors or Prosthetic Groups: pyridoxal 5'-phosphate [Tao08]

Kinetic Parameters:

Substrate
Km (μM)
Citations
L-tryptophan
290.0
[Tao08]

T(opt): 55 °C [Tao08]

pH(opt): 8.8 [Tao08]


Enzymatic reaction of: L-tryptophan:2-oxoglutarate aminotransferase (tryptophan aminotransferase)

Synonyms: L-tryptophan:α-ketoglutarate aminotransferase, L-tryptophan:2-oxoglutarate transaminase, L-tryptophan:α-ketoglutarate transaminase

EC Number: 2.6.1.27

2-oxoglutarate + L-tryptophan <=> L-glutamate + indole-3-pyruvate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

This reaction is reversible.

Alternative Substrates for L-tryptophan: L-methionine [Tao08 ] , L-glutamine [Tao08 ]

In Pathways: indole-3-acetate biosynthesis II

Summary:
Enzymatic assays, in silico docking experiments, and mutant phenotypic analyses all suggest that L-tryptophan is the in vivo substrate for this enzyme [Tao08, Stepanova08]. It is unclear whether pyruvate or 2-oxoglutarate is the more biologically relevant cosubstrate for this enzyme.

Cofactors or Prosthetic Groups: pyridoxal 5'-phosphate [Tao08]


References

Stepanova08: Stepanova AN, Robertson-Hoyt J, Yun J, Benavente LM, Xie DY, Dolezal K, Schlereth A, Jurgens G, Alonso JM (2008). "TAA1-mediated auxin biosynthesis is essential for hormone crosstalk and plant development." Cell 133(1);177-91. PMID: 18394997

Tao08: Tao Y, Ferrer JL, Ljung K, Pojer F, Hong F, Long JA, Li L, Moreno JE, Bowman ME, Ivans LJ, Cheng Y, Lim J, Zhao Y, Ballare CL, Sandberg G, Noel JP, Chory J (2008). "Rapid synthesis of auxin via a new tryptophan-dependent pathway is required for shade avoidance in plants." Cell 133(1);164-76. PMID: 18394996

Truelsen72: Truelsen, T.A. (1972). "Indole-3-Pyruvic Acid as an Intermediate in the Conversion of Tryptophan to Indole-3-Acetic Acid. II. Distribution of Tryptophan Transaminase Activity in Plants." Physiologia Plantarum. 28 (1): 67-70.

Woodward05: Woodward AW, Bartel B (2005). "Auxin: regulation, action, and interaction." Ann Bot (Lond) 95(5);707-35. PMID: 15749753


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 Sun Dec 21, 2014, biocyc11.