Abstract
1. Cytochrome c was guanidinated with O-methylisourea and the number of amino groups reacted in the protein moiety was estimated by the DNP-method of Sanger as well as by the method using the Sakaguchi reaction.
2. Guanidino-derivative of cytochrome c showed the same biological activity in succinic oxidase system, the same absorption spectrum in the reduced state and the same non-reactivity towards carbon monoxide as the original one.
3. The only change observed in the present investigation was the decrease in stability of cytochrome c.
The authors wish to express their thanks to Prof. S. Akabori and Prof. H. Yoshikawa for constant guidances in the course of the work. Thanks are also due to Prof. Y. Yoneyama and Dr. M. Ishimoto for valuable discussions.
