A novel cytotoxic protein, Karatoxin, from the dorsal spines of the redfin velvetfish, Hypodytes rubripinnis

Abstract

A novel cytotoxic protein from the dorsal spines of the redfin velvetfish, Hypodytes rubripinnis, was isolated by a combination of affinity chromatography techniques. The 110-kDa glycoprotein is named Karatoxin. The N-terminal partial amino acid sequence of intact 76-kDa sub-unit of Karatoxin was analyzed as follows: DQHDDxPxxAPDPG. The 76-kDa sub-unit was determined to have mannose moieties. Karatoxin exhibited cytotoxic activity on murine P388 leukemic cells. Furthermore, Karatoxin induced mitogenic stimulation on murine splenocytes. These results suggest that the redfin velvetfish, H. rubripinnis, may be a novel resource for biologically active substances.

Keywords::

• Cytotoxic activity
• dorsal venom
• Karatoxin
• lectin
• mitogenic activity
• redfin velvetfish

Acknowledgements

The authors wish to express appreciation to the late Dr Nagasaka for graciously providing funds and constant encouragement. We also thank Ms E. Ohama for her assistance in collecting the fish samples. This work was supported in part by a Grant-Aid from the University of Tokushima.

Declaration of interest: The authors declare that there are no conflicts of interest.