Porphyrin metabolism in lead and mercury treated bajra (Pennisetum typhoideum) seedlings.
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Date
1990-12
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Abstract
Lead and mercury inhibited porphyrin biosynthesis significantly in the
germinating seeds of bajra (Pennisetum typhoideum). Both 5-aminolevulinic acid
dehydratase and porphobilinogen deaminase activities were inhibited by these metals. A
comparative study of the inhibition of these two enzymes under in vivo and in vitro
conditions showed that 5-aminolevulinic acid dehydratase is the major site of action of
heavy metals in porphyrin biosynthesis. Further, over-all production of porphyrins viz.,
protoporphyrin-IX, Mg-protoporphyrin (ester) and protochlorophyllide was repressed by
lead and mercury in both light and dark grown seedlings. Similarly, chlorophyll a and
chlorophyll b and total chlorophyll contents in dark-grown seedlings were also
significantly decreased, suggesting the impairment of chlorophyll biosynthesis by lead and
mercury in germinating seedlings.
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Keywords
Bajra (Pennisetum typhoideum L.), ALA dehydratase, PBG deaminase, porphyrins, heavy metals
Citation
Prasad D D K, Prasad A R K. Porphyrin metabolism in lead and mercury treated bajra (Pennisetum typhoideum) seedlings. Journal of Biosciences. 1990 Dec; 15(4): 271-279.