Browsing by Subject "Oligomerization"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Publication
    Embargo
    Characterization of the stability of Vibrio fluvialis JS17 amine transaminase
    (ELSEVIER, 2018) Chen, Shan; Campillo-Brocal, Jonatan C.; Berglund, Per; Humble, Maria Svedendahl; Genética y Microbiología
    The amine transaminase from Vibrio fluvialis (Vf-ATA) is an attractive enzyme with applications within Biocatalysis for the preparation of chiral amines. Various catalytic properties of Vf-ATA have been investigated, but a biophysical characterization of its stability has been lacking. Today, the industrial application of Vf-ATA is limited by its low operational stability. In order to enhance the knowledge regarding the structural stability of ATAs, general characterizations of different ATAs are required. In this work, the stability of Vf-ATA was explored. First, the affinity between enzyme and pyridoxal-5'-phosphate (PLP) (KD value of 7.9 μM) was determined. Addition of PLP to enzyme preparations significantly improved the enzyme thermal stability by preventing enzyme unfolding. With the aim to understand if this was due to the PLP phosphate group coordination into the phosphate group binding cup, the effect of phosphate buffer on the enzyme stability was compared to HEPES buffer. Low concentrations of phosphate buffer showed a positive effect on the enzyme initial activity, while higher phosphate buffer concentrations prevented cofactor dissociation. Additionally, the effects of various amine or ketone substrates on the enzyme stability were explored. All tested amines caused a concentration dependent enzyme inactivation, while the corresponding ketones showed no or stabilizing effects. The enzyme inactivation due to the presence of amine can be connected to the formation of PMP, which forms in the presence of amines in the absence of ketone. Since PMP is not covalently bound to the enzyme, it could readily leave the enzyme upon formation. Exploring the different stability effects of cofactor, substrates, additives and buffer system on ATAs seems to be important in order to understand and improve the general performance of ATAs.
  • Thumbnail Image
    Publication
    Open Access
    The protein acetyltransferase PatZ from Escherichia coli is regulated by autoacetylation-induced oligomerization
    (2015) Castaño Cerezo, Sara; Bernal Sanchez, Vicente; Manjón Rubio, Antonio; Fernández Espín, Vanesa; García de la Torre, José; Cánovas Díaz, Manuel; Diego Puente, Teresa de; Gallego Jara, Julia; Bioquímica y Biología Molecular B e Inmunología
    Background: PatZ is the main Escherichia coli acetyltransferase and control acetyl-CoA synthetase (Acs) activity. Results: The kinetic and structural PatZ oligomer characteristics were determined. Conclusion: PatZ is a stable tetramer and forms an active octamer by autoacetylation to increase its stability. Significance: PTMs by acetylation have structural and functional roles in the cell.