Porphyrinsynthesis in isolated particles from tissue cultures of tobacco.

Particles from green and white tissue cultures of Nicotiana tabacum were fractionated by differential and density gradient centrifugation. Besides mitochondria, microbodies and (broken) chloroplasts particles were found able to metabolize 5-amino-levulinate to porphobilinogen and porphobilinogen to uroporphyrinogen. Succinyl-CoA was not synthetized by them but by mitochondria. The porphyrin forming particles had a density of about 1.21 g/cm3 and were accumulated in fractions between mitochondria (1.19 g/cm3) and microbodies (1.23 g/cm3). Small differencies in density were found between particles from white and green tissue cultures. The data available suggest that the porphyrin synthetizing particles are proplastids or leucoplasts.