Plant tissue biosensors for the determination of biogenic diamines and of their amino acid precursors: effect of carbonic anhydrase

A new class of plant tissue biosensors has been set up and applied to the determination of biogenic diamines. All the biosensors presented in this work are based on the amperometric determination of H2O2 produced by the enzymatic oxidation of diamines (putrescine and cadaverine) by the diamine oxidase (DAO) contained in the cotyledon of legumes (pea and lentil). Putrescine and cadaverine were quantitatively determined by means of these plant tissue electrodes in a range of concentrations between 0.5 and 320 μM and between 0.5 and 200 μM, respectively. The same lentil tissue-based sensor was then used, in combination with a lysine decarboxylase (LDC) membrane, for the realization of a hybrid enzyme electrode for the determination of lysine. The performances of the sensor here proposed, tested in lysine standard solutions, were comparable to those of traditional lysine bienzyme electrodes. A similar enzyme electrode was assembled for the determination of ornithine: in this case the lentil tissue diamine oxidase sensor was used in combination with an adequate amount of ornithine decarboxylase (ODC), added directly into the measuring cell. The effect of carbonic anhydrase (CA) on the speed of the LDC- and ODC-catalysed reactions was also evaluated. The synergistic interaction observed between the decarboxylation reaction, operated by either LDC or ODC, and the faciliated transport of CO2, operated by CA, is discussed both in terms of its analytical relevance and of its broader physiopathologic implications.