MECHANISM OF ALUMINUM-INDUCED PORPHYRIN SYNTHESIS IN BACTERIA

In previous studies, aluminium was found to retard bacterial growth an d enhance porphyrin formation in Arthrobacter aurescens RS-2, The aim of this study was to establish the mechanism of action of aluminium wh ich leads to increased porphyrin production, Cultures of Arthrobacter aurescens RS-2 were incubated in the absence and presence of 0.74 mM a luminium, After 6 and 24 h of incubation, various parameters of the ha em biosynthetic pathway were determined, After 6 h of incubation with aluminium, the activities of the enzymes aminolevulinate synthase (ALA S), aminolevulinate dehydratase (ALAD), porphobilinogen deaminase (PBG D) and uroporphyrinogen decarboxylase (UROD) were increased by 120, 17 0, 190 and 203%, respectively, while that of ferrochelatase (FC) was f ound to be unchanged, However, after 24 h of incubation, no change in the activities of ALAS and ALAD was noted, while an about 2-fold incre ase in PBGD and UROD activities were observed, FC activity was decreas ed by 63%, It was concluded that aluminium exerts its effect by induci ng the enzymes PBGD and UROD rather than by a direct or indirect effec t on ALAS, Its effect on the final step in the haem biosynthetic pathw ay is discussed.