RESUMO
Tyrosine phenol-lyase (TPL) catalyzes the reversible cleavage of l-tyrosine to phenol, pyruvate and ammonia. When pyrocatechol is substituted for phenol, l-dihydroxyphenylalanine (l-DOPA) is produced. The TPL-catalyzed route was regarded as the most economic process for l-DOPA production. In this study, a novel TPL from Fusobacterium nucleatum (Fn-TPL) was successfully overexpressed in Escherichia coli and screened for l-DOPA synthesis with a specific activity of 2.69Umg-1. Fn-TPL was found to be a tetramer, and the optimal temperature and pH for α, ß-elimination of l-tyrosine was 60°C and pH 8.5, respectively. The enzyme showed broad substrate specificity toward natural and synthetic l-amino acids. Kinetic analysis suggested that the kcat/Km value for l-tyrosine decomposition was much higher than that for l-DOPA decomposition, while Fn-TPL exhibited similar catalytic efficiency for synthesis of l-tyrosine and l-DOPA. With whole cells of recombinant E. coli as biocatalyst, l-DOPA yield reached 110gL-1 with a pyrocatechol conversion of 95%, which was comparable to the reported highest level. The results demonstrated the great potential of Fn-TPL for industrial production of l-DOPA.
Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Fusobacterium nucleatum/enzimologia , Levodopa/biossíntese , Tirosina Fenol-Liase/química , Tirosina Fenol-Liase/metabolismo , Proteínas de Bactérias/genética , Biocatálise , Biotecnologia , Escherichia coli/enzimologia , Escherichia coli/genética , Fusobacterium nucleatum/genética , Concentração de Íons de Hidrogênio , Microbiologia Industrial , Cinética , Estrutura Quaternária de Proteína , Fosfato de Piridoxal/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidade por Substrato , Temperatura , Tirosina Fenol-Liase/genéticaRESUMO
This study was aimed to establish the matching method of hemolytic test in vitro, and to guide the transfusion treatment for puerpera with acute hemolytic disease. The donor's erythrocytes were sensibilized by all the antibodies in plasma of patient in vitro and were added with complement, after incubation for 6.5 hours at 38 °C, the hemolysis or no hemolysis were observed. It is safe to transfuse if the hemolysis did not occur. The results showed that when the matching difficulty happened to puerpera with acute hemolytic disease, the compatible donor could be screened by hemolytic test in vitro. There were no untoward effects after transfusion of 6 U leukocyte-depleted erythrocyte suspension. The all hemoglobin, total bilirubins, indirect bilirubin, reticulocyte, D-dimex and so on were rapidly improved in patient after transfusion , showing obvious clinical efficacy of treatment. It is concluded that when the matching results can not judge accurately compatible or incompatible through the routine method of cross matching, the agglutinated and no-hemolytic erythrocytes can be screened by hemolytic test in vitro and can be transfused with good efficacy; the hemoglobin level can be promoted rapidly, and no untoward effects occur.
