THESE Maryse Bonnin Jusserand - Université de Bourgogne

Résultats
Figure 5: Effect of pH (3.4-7) and temperature (25-40°C) on recombinant ornithine
decarboxylase activity. Data are the means ±SD of three independent experiments.
The behavior presented by this enzyme is rather different from that of E. coli constitutive
ODC, whose optimal pH is 8.1. Also the optimal pH of the lysine decarboxylase (LDC) of S.
ruminantium (GI 2897824) is 6.0 and pH stability for enzymatic activity ranges between 5.5
and 8.0 (19).
Km and Vmax values for the ornithine decarboxylase were calculated from the plot initial
velocity vs. substrate concentration (Fig. 6). The Km and Vmax values were respectively 1 mM
and 0.57 U mg -1 proteins. Vmax and Km for ornithine decarboxylase are the lowest reported
compared to the kinetic constants of Lactobacillus 30a which are respectively 200 U mg -1
proteins and 1.7 mM (8) and S. ruminantium showing a Vmax for L-ornithine of 6.71 U mg -1
and a Km of 1.2 mM (19), while Km of E. coli constitutive ODC is 5.6 mM.
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