SHINNAR*, Ann E.*; MUSICH, Christine; SHU, Joan; WILLEMSEN, Hege M.; STOKNES, Iren S.; KJERSTAD, Margareth; Barnard College, Columbia Univ., NY, NY; Barnard College, NY, NY; Barnard College, NY, NY; M�re Research, Aalesund, Norway; M�re Research, Aalesund, Norway; M�re Research, Aalesund, Norway: Biosynthesis of Squalamine in Various Species of Shark and Rabbitfish

Squalamine is an aminosterol originally isolated from the spiny dogfish shark, Squalus acanthias. This amphipathic, zwitterionic compound displays broad spectrum antimicrobial activity and is an angiogenesis inhibitor. Squalamine is particularly abundant in spiny dogfish liver, making that a good tissue for investigating the biosynthetic pathway of this unusual steroid. After cellular fractionation of homogenized spiny dogfish liver via ultracentrifugation, squalamine was detected in the total membrane (TM) fraction. In order to investigate the distribution of squalamine in other cartilaginous fish, a mini-scale extraction scheme was devised. TM fractions isolated from livers of 16 species belonging to four orders of Chondrichthyes were processed in parallel using organic solvent extraction, followed by solid phase extraction (SPE) with C18 disk cartridges. After step-eluting SPE, antimicrobial activity was tested by the clearing zone assay against lawns of Escherichia coli, Staphylococcus aureus, and Candida albicans. Antimicrobial activity was observed in liver extracts from the spiny dogfish shark and 5 other sharks of the order Squaliformes. TM samples from 4 species of Carcharhiniformes, 3 species of Lamniformes, and 3 species of Chimaeriformes showed no antimicrobial activity. Our initial survey suggests that squalamine production is not universal among cartilaginous fish, but varies among orders of Chondrichthyes. Active production of squalene, known among squaliform sharks, might be a key requirement in the biosynthetic pathway that branches to yield squalamine.