The synthesis of porphyrins and bacteriochlorophyll in cell suspensions of Rhodopseudomonas spheroides

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Abstract
Cell suspensions of R. spheroides convert glycine and alpha-oxoglutarate into porphyrins. An oxidizable substrate, Mg, ammonium and Mn ions are required for maximum synthesis. Porphyrins are formed from glycine and alpha- oxoglutarate only in the light. Aerobiosis suppresses synthesis in light; no porphyrins are formed aerobically in the dark. Cells form porphyrin from glycine and alpha-oxoglutarate only when nicotinic acid, thiamine or biotion are added to the incuba- tion systems, delta-Aminolaevulic acid is converted into porphyrins, apparently as a product of condensation between glycine and alpha-oxoglutarate or derivatives. Porphobilinogen accumulates during the early stages of incubation with delta- aminolaevulic acid and later disappears, delta-Aminolaevulic acid is converted into porphyrins anaerobically in light or aerobically in the dark. In the light, maximum formation of porphyrins occurs in the presence of phosphate and Mg ions only; under aerobic conditions an oxidizable substrate is also needed. Iron salts almost completely suppress porphyrin formation from glycine and alpha-oxoglutarate, but increase the formation of bacteriochlorophyll and haem components. Increase in these accounts for only 10 and 1%, respectively, of the porphyrins which fail to appear. Iron does not suppress porphyrin synthesis from delta-aminolaevuluc acid. Coproporphy- rin III is the major component of theporphyrins formed from glycine and alpha-oxoglutarate and from delta-aminolaevulic acid. Uroporphyrins I and III are also formed in small quantities, and traces of other porphyrins containing 3 and 6 carboxyl groups can be* detected by chromatography. Protoporphyrin, comprising 20- 30% of the total porphyrins, is formed from delta-aminolaevulic acid anaerobically in the light provided that Fe and an oxidizable substrate are present. Aerobically grown cells form proto porphyrin from delta-aminolaevulic acid under aerobic conditions in the absence of Fe. It is suggested that porphyrin formation by R. spheroides is associated with synthesis of bacterio-chlorophyll and that Fe is concerned in the conversion of por-phyrins or derivatives into bacteriochlorophyll.