Effect of light and oxygen on neocarzinostatin stability and DNA-cleaving activity

The in vitro DNA-cleaving activity of neocarzinostatin, a protein antibiotic, is strongly but reversibly inhibited by anaerobiosis. Half-maximal activity is seen in the presence of 0.25 mM O2. The stability of neocarzinostatin, as demonstrated by its ability to cleave DNA, is significantly reduced in light. Inactivation by light is complete and irreversible.