THESE Maryse Bonnin Jusserand - Université de Bourgogne

1/Vi
25
20
15
10
5
0
y = 1,820x + 1,773
R² = 0,999
0 2 4 6 8 10 12
Résultats
Figure 6: Lineweaver-Burk plots of ornithine decarboxylase (representative of three
experiments). Vi (µg min -1 mg -1 enzyme), S ([L-ornithine] mM).
It can be seen that recombinant decarboxylase is more selective for ornithine, despite
presenting a lower Vmax for this substrate. The low affinity constant could reflect the low
abundance of ornithine in wine (7), the natural habitat of O. oeni.
The substrate specificity of ornithine decarboxylase was investigated using various synthetic
substrates which are other diaminocarboxylic acids with NH2(CH2)nCH(NH2)COOH as the
general chemical structure: D-ornithine, L-arginine, L-glutamine, L-histidine, L-citrulline, L-
lysine, L-2,4-diaminobutyric acid, 6-aminocaproic acid and 2,6-diaminopimelic acid.
However, the enzyme has no activity towards any of the substrates tested. In contrast to other
bacteria such as S. ruminantium (11), ODC from O.oeni has absolute specificity as a
decarboxylase for L-ornithine.
LDC of S. ruminatium shows very low identity (about 10%) with ODC of O. oeni. This
protein is different in size. Indeed ODC from this bacterium is shorter: 393 amino acids.
Moreover S. ruminantium LDC was reported to be closer to eukaryotic ornithine
decarboxylase than to prokaryotic ODC (20). Regarding S. epidermidis ODC, this enzyme
shows better identity (24%) with the lysine/arginine/ornithine decarboxylase of
Sinorhizobium meliloti (GI 193782595) than with the lysine/ornithine decarboxylase of S.
ruminantium (17%). This point can be explained by the fact that S. epidermidis and S. meliloti
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