抄録
A facultative methylotroph, Protaminobacter ruber, classified as nonphotosynthetic bacteria formed bacteriochlorophyll as well as vitamin B_<12> and cytochrome. The mode of bacteriochlorophyll formation was very unique, since oxygen was absolutely required for its synthesis and continuous exposure to light blocked it completely even at very low light intensity. Bacteriochlorophyll was not only formed in the dark, but also inducibly formed most abundantly by cultivating the bacterium in the dark after exposure to light during the relatively early stage of the growth. The regulation of tetrapyrrole biosyntheses including bacteriochlorophyll synthesis was examined in terms of 5-aminolevulinic acid (ALA) synthase. The two fractions of ALA synthase activity were obtained by Sepharose 6B column chromatography and the presence of an isozyme was demonstrated by the difference of two fractions in molecular weight, optimal pH and the effect of end-product such as hemin and vitamin B_<12> derivatives. One enzyme was formed inducibly in fairly good agreement with bacteriochlorophyll formation. The other constitutive enzyme seems to participate mainly in vitamin B_<12> and cytochrome formation.
