4-Aminobutyrate:2-oxoglutarate aminotransferase from Candida. Purification and properties.
An enzyme which catalyzes the transamination of 4-aminobutyrate with 2-oxoglutarate was purified 588-fold to homogeneity from Candida guilliermondii var. membranaefaciens, grown with 4-aminobutyrate as sole source of nitrogen. An apparent relative molecular mass of 107,000 was estimated by gel filtration. The enzyme was found to be a dimer made up of two subunits identical in molecular mass (Mr 55,000). The enzyme has a maximum activity in the pH range 7.8-8.0 and a temperature optimum of 45 degrees C. 2-Oxoglutarate protects the enzyme from heat inactivation better than pyridoxal 5'-phosphate. The absorption spectrum of the enzyme exhibits two maxima at 412 nm and 330 nm. The purified enzyme catalyzes the transamination of omega-amino acids; 4-aminobutyrate is the best amino donor and low activity is observed with beta-alanine. The Michaelis constants are 1.5 mM for 2-oxoglutarate and 2.3 mM for 4-aminobutyrate. Several amino acids, such as alpha,beta-alanine and 2-aminobutyrate, are inhibitors (Ki = 38.7 mM, Ki = 35.5 mM and Ki = 33.2 mM respectively). Propionic and butyric acids are also inhibitors (Ki = 3 mM and Ki = 2 mM).
Der Garabedian
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Lotti
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Vermeersch
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D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D000409:Alanine / Q000494:pharmacology; D000613:Aminobutyrates / Q000494:pharmacology; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D002175:Candida / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007700:Kinetics; D008970:Molecular Weight; D011422:Propionates / Q000494:pharmacology; D011732:Pyridoxal Phosphate / Q000032:analysis; D013379:Substrate Specificity; D013696:Temperature
D000613:Aminobutyrates; D002087:Butyrates; D011422:Propionates; D020148:Butyric Acid; D011732:Pyridoxal Phosphate; C012223:alpha-aminobutyric acid; D000612:4-Aminobutyrate Transaminase; C029658:propionic acid; D000409:Alanine