L-amino acid oxidases (EC 18.104.22.168, L-aao) are flavoenzymes that catalyse the stereospecific deamination of an L-amino acid to their corresponding α-keto acid with the production of hydrogen peroxide and ammonia. These enzymes are widely distributed across diverse phyla from bacteria, fungi to mammals and many venomous snakes. Although they are mainly involved in cellular amino acid catabolism, many other physiological functions are attributed to L-aao including their antibacterial property and ability to protect from infection. L-aao has also been correlated with penicillin production, violacein synthesis and biofilm development and cell dispersal. Snake venom L-aaos are studied extensively for their ability to induce apoptosis, aggregate platelets, induce haemorrhage, edema and many other toxic effects. L-aaos have been characterized biochemically and found to differ in terms of biochemical parameters not only among different species but also among members of the same species. L-aao act on L-amino acids, preferentially basic, aromatic and aliphatic L-amino acids. The snake venom enzyme shows broad oxidizing activity towards aromatic and hydrophobic L- amino acids such as leucine, phenylalanine and isoleucine. L-aaos have practical value in biochemical and chemical investigations as they have been used to destroy Lisomer of a racemic DL-amino acid and thus yield an optically pure preparation of the D- isomer. As such, L-aao finds numerous applications as catalysts in biotransformation and for production of keto acids. L-aao has also been used for the determination of L-amino acids as part of biosensors. L-amino acids are reported to be found in physiological fluids of patients with certain diseases and disorders. In addition, the content of certain amino acids essentially controls the nutritional quality of the food. L-aao is useful in this aspect by development of biosensors to detect the L-amino acids. Snake venom L-aaos are known to induce apoptosis and antibacterial effects mediated by the hydrogen peroxide produced during the L-aao reaction. The hydrogen peroxide induces oxidative stress which in turn activates the heat shock proteins and initiates an array of functions ultimately leading to apoptosis and cell death. In this aspect, L-aao can be greatly useful for the development of efficient therapeutics and drugs to control tumor cells, bacterial, leishmanicidal, viral and protozoal infections. L-aao is also reported to display dose dependent inhibition on HIV-1 infection and replication and as such can be studied for development of anti HIV medicine.