The 2.8-kb sequence of cDNA encoding southeastern diamondback rattlesnake venom L-amino acid oxidase was determined. A translated single open reading frame revealed a 58.7-kDa polypeptide containing a signal sequence and FAD binding motif. The protein similarity search and analysis showed that the snake L-amino acid oxidase possesses the highest degree of homology (37% of identity) with a protein encoded by the mouse B cell interleukin 4-induced Fig1 gene. (C) 1998 Academic Press.