PHOTOREACTIVATING ENZYME FROM STREPTOMYCES GRISEUS—IV. ON THE NATURE OF THE CHROMOPHORIC COFACTOR IN STREPTOMYCES GRISEUS PHOTOREACTIVATING ENZYME

Abstract— A structure for the chromophoric part of the intrinsic cofactor of Streptomyces griseus photo-reactivating enzyme is suggested on the basis of absorption and fluorescence spectra of cofactor and reference compounds at various pH. The essential chromogenic part of this cofactor is proposed to be a 7,8-didemethy]-8-hydroxy-5-deazaflavin derivative (Ia).
From whole S. griseus cells a compound SF420 (Ic) was isolated which contains the same chromophoric group. This compound sensitizes the splitting of thymine dimers when irradiated with blue light, supporting the structure proposed for the photoreactivating enzyme cofactor.