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Role of light in the biosynthesis and turnover of photosynthetic fructose‐1, 6‐bisphosphatase in pea ( Pisum sativum L.) seedlings
Author(s) -
SAHRAWY M.,
CHUECA A.,
HERMOSO R.,
LÁZARO J. J.,
GORGÉ J. LÓPEZ
Publication year - 1990
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1990.tb00491.x
Subject(s) - pisum , fructose 1,6 bisphosphatase , sativum , photosynthesis , etiolation , biochemistry , enzyme , biology , photorespiration , enzyme assay , fructose , ferredoxin , botany
summary Photosynthetic fructose‐ 1, 6‐bisphosphatase (FBPase) determined immunologically by ELISA undergoes a sharp increase when etiolated pea ( Pisum sativum L. cv. Lincoln) seedlings are illuminated for 24 h. The rise of enzyme activity appears slower than that of FBPase protein, which means an earlier synthesis of a precursor or some other immunologically related but inactive form of the enzyme. A second possibility is a delayed synthesis of a factor – i.e. a component of the ferredoxin‐thioredoxin activation system – necessary for the expression of the enzyme activity. With more extended illumination times, the highest FBPase content, as well as maximum activity, was obtained after 4 d of light exposure, the former representing 0.66 % of the total soluble protein. After that time, a decrease of both FBPase protein and enzyme activity was observed, probably as a consequence of a premature senescence promoted by such an extended and continuous light exposure. A maximum FBPase labelling was obtained at 6.5 h after leaf application of a [ 35 S]methionine pulse to etiolated pea seedlings, which were then continuously illuminated. From the pattern of the radioactive decay of FBPase labelling, a half‐life of 14 h was calculated for this photosynthetic enzyme.