Protoheme Turnover and Chlorophyll Synthesis in Greening Barley Tissue 1

Studies in which 14 C-labeled precursors were fed to etiolated barley leaves ( Hordeum vulgare L. var. Proctor) yielded chlorophyll and protoheme having similar specific radioactivities. These findings indicate: ( a ) there appears to be a rapid turnover of protoheme in the absence of net synthesis;...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1975-03, Vol.55 (3), p.485-490
Main Authors: Castelfranco, Paul A., Jones, Owen T. G.
Format: Article
Language:English
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Summary:Studies in which 14 C-labeled precursors were fed to etiolated barley leaves ( Hordeum vulgare L. var. Proctor) yielded chlorophyll and protoheme having similar specific radioactivities. These findings indicate: ( a ) there appears to be a rapid turnover of protoheme in the absence of net synthesis; ( b ) both pigments probably originate from a single 5-aminolevulinic acid pool; ( c ) the efficient utilization of glutamate-1- 14 C and the relatively poor utilization of glycine-2- 14 C suggest that 5-aminolevulinic acid is probably synthesized by a pathway other than 5-aminolevulinic acid synthetase (succinyl CoA-glycine succinyltransferase) in agreement with previously published work; ( d ) protoheme turnover appears to be faster under conditions which allow for rapid chlorophyll accumulation; ( e ) difference spectra indicate that mitochondrial cytochromes make a relatively minor contribution to the total heme in barley leaves. These findings are discussed in the light of current knowledge about tetrapyrrole regulation in photosynthetic organisms.
ISSN:0032-0889
1532-2548