Protoheme turnover and chlorophyll synthesis in greening barley tissue

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

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1975-03, Vol.55 (3), p.485-490
Main Authors: Castelfranco, Paul A., Owen T. G. Jones
Format: Article
Language:English
Subjects:
Alcohols
Barley
Chlorophylls
Ethers
Greening
Plants
Porphyrins
Protoporphyrins
Pyridines
Radioactive decay
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Summary:Studies in which 14C-labeled precursors were fed to etiolated barley leaves (Hordeum vulgare L. var. Proctor) yielded chlorophyll and protoheme having similalr 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-amino-levulinic acid pool; (c) the efficient utilization of glutamate-1-14C and the relatively poor utilization of glycine-2-14C 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
DOI:10.1104/pp.55.3.485