A novel thermostable alkaline histamine oxidase from Glutamicibacter sp. N1A3101, induced by histamine and its analogue betahistine.

Biogenic amines (BAs) are low molecular weight organic bases formed by natural amino acids decarboxylation and trigger an array of toxicological effects in humans and animals. Bacterial amine oxidases enzymes are determined as practical tools to implement the rapid quantification of BAs in foods. Our study set out to obtain a new efficient, amine oxidase enzyme for developing new enzyme-based quantification of histamine. The soils from different sources were screened using histamine as sole carbon and nitrogen sources, and histamine oxidase producing bacteria were selected and identified using specific primers for histamine oxidase (HOD) gene. The HOD gene of six strains, out of 26 isolated histamine-utilizing bacteria, were amplified using our designed primers. The HOD enzyme from Glutamicibacter sp. N1A3101, isolated from nettle soil, was found to be thermostable and showed the highest substrate specificity toward the histamine and with no detected activity in the presence of putrescine, cadaverine, spermine, and spermidine. Its oxidation activity toward tyramine was lower than other HOD reported so far. The isolated enzyme was stable at 60 °C for 30 min and showed pH stability ranging from 6 to 9. Furthermore, we indicated the induction of identified HOD activity in the presence of betahistine as well, with nearly equal efficiency and without the consumption of the substrate.