Synthesis of porphyrins by cell suspensions of Tetrahymena vorax: effect of members of the vitamin B group

Abstract

Suspensions of T. vorax synthesize porphyrins when incubated aerobically at 37[degree] with glycine and fumarate; they also convert [delta]-aminolaevulic acid into porphyrins. Synthesis from glycine by organisms harvested from media containing growth-limiting concentrations of pyridoxal or pantothenate is reduced to 30% or less of that achieved by cells grown at optimum concentrations of these vitamins. Cells deficient in riboflavin, nicotinic acid, thiamine or thioctic acid also form less porphyrin from glycine than do normal cells. Synthesis from [delta]-aminolaevulic acid by cells deficient in riboflavin is reduced; deficiency in the other vitamins does not decrease the amount of porphyrins formed from this substrate. The porphyrins formed from either glycine or [delta]-aminolaevulic acid consist of a mixture of uroporphyrin HI, protoporphyrin and coproporphyrin III. Cells deficient in pantothenate form less protoporphyrin than do normal cells. Organisms harvested from media containing added iron salts do not form porphyrins from glycine, but do so from 6 -aminolaevulic acid. Such cells form more protoporphyrin from this substrate than do organisms grown without added iron. It is concluded that pyridoxal and pantothenate may be concerned directly in the primary stage of porphyrin biosynthesis, which involves condensation between glycine and a 4-C intermediate.