Production of the apoptotic cellular mediator 4-Methylthio-2-oxobutyric acid by using an enzymatic stirred tank reactor with in situ product removal.
d-Amino acid oxidase (DAAO) was used to study the oxidative deamination of racemic mixtures of d,l-methionine in its soluble and immobilized forms and thus obtain the corresponding alpha-keto acid. The soluble enzyme form was obtained from a Trigonopsis variabilis CBS 4095 extract, free of l-amino acid oxidase, and was co-immobilized with a 200-fold excess of catalase to avoid the undesirable side reaction of H2O2 with the alpha-keto acid, which would otherwise render its corresponding decarboxylated acid, the 3-methylthiopropionic acid (MTPA). With this biocatalyst, quantitative conversion (>98%) of d-methionine into the alpha-keto acid 4-methylthio-2-oxobutyric acid (MTOB) and into MTPA was achieved using 5 mg.mL(-1) of biocatalyst at pH 8.0, 25 degrees C, and pure oxygen at 3 vvm. A stirred tank reactor with in situ product removal (STR-ISPR) was developed to avoid conversion of MTOB into MTPA. The reaction medium was re-circulated through a strong anion exchange column (Amberlite IRA-400). This resulted in the complete removal of MTOB from the reaction medium. After the reaction, the reaction products were eluted sequentially with water (l-methionine), 10 mM HCl (MTPA), and 0.5 M HCl (MTOB). After elution, MTOB was crystallized to its sodium salt.
García-García
Miguel
M
Department of Biochemistry and Molecular Biology-A, Faculty of Biology, University of Murcia, Campus Espinardo, E-30071 Murcia, Spain.
Martínez-Martínez
Irene
I
Sánchez-Ferrer
Alvaro
A
García-Carmona
Francisco
F
D001203:Ascomycota / Q000201:enzymology; D019149:Bioreactors; D003605:D-Amino-Acid Oxidase / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure
C014632:2-keto-4-methylthiobutyric acid; D008715:Methionine; D003605:D-Amino-Acid Oxidase