Abstract
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 (TanB(Fnp)). TanB(Fnp) 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. TanB(Fnp) 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 °C. TanB(Fnp) also shows a wide temperature range of activity, maintaining above 80% of its maximum activity between 22 and 55 °C. The use of a panel of 27 esters of phenolic acids demonstrated activity of TanB(Fnp) only against esters of gallic and protocatechuic acid, including tannic acid, gallocatechin gallate and epigallocatechin gallate. Overall, TanB(Fnp) 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 TanB(Fnp) 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.