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PMID:236311

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Citation

Mavrides, C and Orr, W (1975) Multispecific aspartate and aromatic amino acid aminotransferases in Escherichia coli. J. Biol. Chem. 250:4128-33

Abstract

Two aminotransferases from Escherichia coli were purified to homogeneity by the criterion of gel electrophoresis. The first (enzyme A) is active on L-aspartic acid, L-tyrosine, L-phenylalanine, and L-tryptophan; the second (enzyme B) is active on the aromatic amiono acids. Enzyme A is identical in substrate specificity with transaminase A and is mainly an aspartate aminotransferase; enzyme B has never been described before and is an aromatic amino acid aminotransferase. The two enzymes are different in the Vmax and Km values with their common substrates and pyridoxal phosphate, in heat stability (enzyme A being heat-stable and enzyme B being heat-labile at 55 degrees) and in pH optima with the amino acid substrates. They are similar in their amino acid composition, each enzyme appears to consist of two subunits, and enzyme B may be converted to enzyme A by controlled proteolysis with subtilsin. The conversion was detected by the generation of new aspartate aminotransferase activity from enzyme B and was further verified by identification by acrylamide gel electrophoresis of the newly formed enzyme A. The two enzymes appear to be products of two genes different in a small, probably terminal, nucleotide sequence.

Links

PubMed

Keywords

Amino Acids/analysis; Apoenzymes; Aspartate Aminotransferases/metabolism; Chromatography, DEAE-Cellulose; Drug Stability; Electrophoresis, Polyacrylamide Gel; Escherichia coli/enzymology; Hot Temperature; Hydrogen-Ion Concentration; Isoelectric Focusing; Kinetics; Phenylalanine; Time Factors; Transaminases/isolation & purification; Transaminases/metabolism; Tryptophan; Tyrosine Transaminase/metabolism

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ECOLI:TYRB

acts_upstream_of_or_within

GO:0019292: tyrosine biosynthetic process from chorismate via 4-hydroxyphenylpyruvate

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

ECOLI:TYRB

acts_upstream_of_or_within

GO:0033585: L-phenylalanine biosynthetic process from chorismate via phenylpyruvate

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

ECOLI:TYRB

enables

GO:0004838: L-tyrosine:2-oxoglutarate aminotransferase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

ECOLI:TYRB

enables

GO:0008793: aromatic-amino-acid:2-oxoglutarate aminotransferase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

ECOLI:TYRB

involved_in

GO:0019292: tyrosine biosynthetic process from chorismate via 4-hydroxyphenylpyruvate

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

ECOLI:TYRB

involved_in

GO:0033585: L-phenylalanine biosynthetic process from chorismate via phenylpyruvate

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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