L-Amino acid oxidases: Properties and molecular mechanisms of action

During the last 10–15 years L-amino acid oxidases (LAAO) are intensively studied due to their diverse effects on various biological objects. The review summarized information about sources, structure, physicochemical, and catalytic properties of LAAO as well as data on their antibacterial, antifungal, antiprotozoal, antiviral, antiproliferative, and antitumor effects, and on ambiguous effects on platelet aggregation. Special attention is paid to analysis of literature data on elucidation of molecular mechanisms of the LAAO action. It is proposed that the unique properties of LAAO are associated the decrease of L-amino acid levels, including the essential amino acids and formation of hydrogen peroxide, which indirectly (via reactive oxygen species, ROS) acts on cells and triggers biological mechanisms of apoptosis and necroses. The presence of carbohydrate components in LAAO molecules promotes enzyme attachment to the cell surface and creation of high local concentrations of hydrogen peroxide. The wide range of biological effects of LAAO in vivo is usually associated with their functional importance. For example, in the mouse brain the LAAO-catalyzed reaction is the only reaction for L-lysine degradation, while in the mouse milk LAAO acts as a bactericide agent. Leukocyte LAAO is involved in realization of the systemic anti-infective effect. The protective action is also attributed to the oxidases from the other numerous sources including microscopic fungi, snake venoms and sea inhabitants.