Abstract
The antitumor protein, neocarzinostatin (NCS) is an acidic single-chain molecule, crosslinked by two disulfide bridges, and consists of 109 amino acid residues. In the present study, effects on the aqueous solutioti of NCS by heat, ultraviolet and sunlight, and in the various pH solution were investigated. The present resulti have disclosed the following points:
(1) The kinetic studies of the inactivation in the aqueous solution of NCS indicated that thermal inactivation of NCS was based on the apparent first-order reaction. It was confirmed that ARRHENIUSe xpression was applicable between the rate constant and the temperature. The validity of activity in aqueous NCS solution at pH 5.0 that was reduced from initial concentration (100%) to 90% residual concentration was 13.6 months and 32 months on 10°C and 4°C, respectively.
(2) It was clarified by log κ-pH profile that aqueous NCS solution was most stable at pH 5.0.
(3) The stabilities of NCS were measured in various buffer solution, buffer concentration, isotonic saline and isotonic glucose solution. No significant change in residual activity was observed.
(4) Inactivation rate of NCS solution under sunlight was more faster than thermal one. The mode of inactivation of aqueous NCS solution did not present neither apparent first-order reaction such as heat nor zero-order reaction such as ultraviolet.(5) On the other hand, the mode of inactivation under ultraviolet showed a type of zeroorder reaction, and the inactivation rate was fast as well as the inactivation rate by sunlight.
