In Lactobacillus plantarum the metabolism of hydroxybenzoic and hydroxycinnamic acid derivatives follows a similar two-step pathway, an esterase action followed by a decarboxylation. The L. plantarum esterase genes involved in these reactions have been cloned into pNZ8048 or pT1NX plasmids and transformed into technologically relevant lactic acid bacteria. None of the strains assayed can hydrolyse methyl gallate, a hydroxybenzoic ester. The presence of the L. plantarum tannase encoding genes (tanA(Lp) or tanB(Lp)) on these bacteria conferred their detectable esterase (tannase) activity. Similarly, on hydroxycinnamic compounds, esterase activity for the hydrolysis of ferulic acid was acquired by lactic acid bacteria when L. plantarum esterase (JDM1_1092) was present. This study showed that the heterologous expression of L. plantarum esterase genes involved in the metabolism of phenolic acids allowed the production of healthy compounds which increase the bioavailability of these dietary compounds in food relevant lactic acid bacteria.
Colorectal cancer pathogenesis and progression is associated with the presence of Fusobacterium nucleatum and the reduction of acetylated derivatives of spermidine, as well as dietary components such as tannin-rich foods. We show that a new tannase orthologue of F. nucleatum (TanBF(nn) ) has significant structural differences with its Lactobacillus plantarum counterpart affecting the flap covering the active site and the accessibility of substrates. Crystallographic and molecular dynamics analysis revealed binding of polyamines to a small cavity that connects the active site with the bulk solvent which interact with catalytically indispensable residues. As a result, spermidine and its derivatives, particularly N(8) -acetylated spermidine, inhibit the hydrolytic activity of TanBF(nn) and increase the toxicity of gallotannins to F. nucleatum. Our results support a model in which the balance between the detoxicant activity of TanBF(nn) and the presence of metabolic inhibitors can dictate either conducive or unfavourable conditions for the survival of F. nucleatum.
BACKGROUND: Tannases are tannin-degrading enzymes that have been described in fungi and bacteria as an adaptative mechanism to overcome the stress conditions associated with the presence of these phenolic compounds. RESULTS: We have identified and expressed in E. coli a tannase from the oral microbiota member Fusobacterium nucleatum subs. polymorphum (TanBFnp). TanBFnp is the first tannase identified in an oral pathogen. Sequence analyses revealed that it is closely related to other bacterial tannases. The enzyme exhibits biochemical properties that make it an interesting target for industrial use. TanBFnp has one of the highest specific activities of all bacterial tannases described to date and shows optimal biochemical properties such as a high thermal stability: the enzyme keeps 100% of its activity after prolonged incubations at different temperatures up to 45 degrees C. TanBFnp also shows a wide temperature range of activity, maintaining above 80% of its maximum activity between 22 and 55 degrees C. The use of a panel of 27 esters of phenolic acids demonstrated activity of TanBFnp only against esters of gallic and protocatechuic acid, including tannic acid, gallocatechin gallate and epigallocatechin gallate. Overall, TanBFnp possesses biochemical properties that make the enzyme potentially useful in biotechnological applications. CONCLUSIONS: We have identified and characterized a metabolic enzyme from the oral pathogen Fusobacterium nucleatum subsp. polymorphum. The biochemical properties of TanBFnp suggest that it has a major role in the breakdown of complex food tannins during oral processing. Our results also provide some clues regarding its possible participation on bacterial survival in the oral cavity. Furthermore, the characteristics of this enzyme make it of potential interest for industrial use.
