Diamine oxidase (DAO, histaminase) is known to reduce inflammation due to allergic response to exogeneous/endogenous amines and to be beneficial in topical applications for skin conditions. Foods, especially fermented foods, are an important source of exogeneous amines and deficient/low-activity intestinal DAO may result in increase in the histamine level in plasma and, eventually, in histamine intolerance. Additionally, improper processing/storage of foods may contribute to increase in histamine level in those foods, leading to histamine poisoning, as well as an increase in other biogenic amines’ content. This makes quantitation of biogenic amines in foods important for ensuring the desired quality and freshness, especially in fish/shellfish, and because of their inhibitory effect on histaminase activity. Instrumental methods for biogenic amine detection are expensive and some require derivatization. While amperometric biosensors using DAO are sensitive and inexpensive, their drawback is the high cost and low activity of commercially available DAO. This study presents a green approach to enhance and stabilize DAO from porcine kidney using high hydraulic pressure (HHP). A mechanical procedure is presented in which DAO is compressed in the presence of enzyme-friendly redox species (Cu2+, pyridoxal phosphate, PLP). DAO unfolds partially and refolds, after HHP removal. All modified DAO samples obtained retained activity. Copper ions (intrinsic to DAO) were more beneficial than PLP and shorter compression times resulted in more active enzymes. DAO-friendly redox units entrapped within the 3-D structure of histaminase afford a self-mediated, “wired” DAO which was tested in an amperometric biosensor. The catalytic effect and linearity of the response recommend this biosensor for use in detection of biogenic amines. The procedure presented is simple, avoids toxic mediators/reagents used in enzyme “wiring” and it results in DAO which is molecularly “wired” and able of direct electron transfer. The modified DAO was stable over several months and warrants testing in medical applications as well.
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