RESUMEN
Transaminase responsible for alienating prochiral ketone compound is applicable to asymmetric synthesis of herbicide L-phosphinothricin (L-PPT). In this work, the covalent immobilization of recombinant transaminase from Citrobacter koseri (CkTA) was investigated on different epoxy resins. Using optimum ES-105 support, a higher immobilized activity was obtained via optimizing immobilization process in terms of enzyme loading, coupling time and initial PLP concentration. Crucially, due to blocking unreacted epoxy groups on support surface with amino acids, the reaction temperature of blocked immobilized biocatalyst was enhanced from 37 to 57 °C. Its thermostability at 57 °C was also found to be superior to that of free CkTA. The Km value was shifted from 36.75 mM of free CkTA to 39.87 mM of blocked immobilized biocatalyst, demonstrating that the affinity of enzyme to the substrate has not been apparently altered. Accordingly, the biocatalyst performed the consecutive synthesis of L-PPT for 11 cycles (yields>91%) with retaining more than 91.13% of the initial activity. The seemingly the highest reusability demonstrates this biocatalyst has prospective for reducing the costs of consecutive synthesis of L-PPT with high conversion.
Asunto(s)
Aminobutiratos/síntesis química , Proteínas Bacterianas/química , Citrobacter koseri/enzimología , Enzimas Inmovilizadas/química , Resinas Epoxi/química , Transaminasas/química , Proteínas Bacterianas/genética , Citrobacter koseri/genética , Enzimas Inmovilizadas/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Transaminasas/genéticaRESUMEN
PURPOSE: To compare the cytotoxicity of 5 different dental bonding agents to human periodontal ligament cells(HPDLCs). METHODS: Primary cultured HPDLCs were exposed to different concentrations (100%,50% and 25%) of Super Bond, Clearfil SE Bond, G-Bond, Single Bond2, and Adper Easy One for different times (24 h, 48 h and 72 h). Cytotoxicity of 5 different agents to HPDLCs were observed by MTT method. The data was analyzed using SPSS 19.0 software package. RESULTS: Cytotoxicity of 5 dentin bonding agents to HPDLCs were Super Bond