Diamine oxidase and putrescine oxidase immobilized reactors in flow injection analysis: a comparison in substrate specificity

Enzyme reactors for the determination of biogenic amines have been developed using diamine oxidase (DAO) from porcine kidney and from lentil and putrescine oxidase (PUO) from microorganism (Micrococcus roseus). Determination is based on the electrochemical oxidation of enzymatically produced H2O2 at platinum electrode poised at 600 mV versus Ag/AgCl. The enzymes are immobilized on controlled pore glass beads activated by glutaraldehyde in a small reactor (diameter 5 mm, length 50 mm) and included in a flow injection analysis assembly. The reactor using DAO from porcine kidney as the biochemical component responds mainly to histamine (with a detection limit of 0.5 μM), and it can be used for the evaluation of fish spoilage. The PUO reactor shows a significant response only to putrescine. It is linear in the range 0.07–500 μM. The reactor using DAO from lentil is sensitive to several amines and it could be useful to evaluate a total value. The buffer used for both types of oxidase based sensors is phosphate 0.10 M pH 7.0 containing 0.10 M NaCl.