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Gas exchange in intact isolated chloroplasts from Chlamydomonas reinhardtii during starch degradation in the dark
Author(s) -
Klöck G.,
Sültemeyer D. F.,
Fock H. P.,
Kreuzberg K.
Publication year - 1989
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1989.tb02071.x
Subject(s) - chlamydomonas reinhardtii , chloroplast , chlamydomonas , starch , thylakoid , ferredoxin , biochemistry , photosynthesis , chemistry , oxygen , biology , enzyme , organic chemistry , mutant , gene
During starch degradation in intact isolated chloroplasts from Chlamydomonas reinhardtii gas exchange was studied with a mass spectrometer. Oxygen uptake by intact chloroplasts in the dark never exceeded 1.5% of the starch degradation rate [maximum 15 nmol O 2 (mg Chl) −1 h −1 consumed. 1 000 nmol glucose (mg Chl) −1 h −1 degraded]. Evolution of CO 2 under aerobic conditions [9.8–28 nmol (mg Chl) −1 h −1 ] was stimulated by addition of 0.1–0.5 m M oxaloacetate [393–425 nmol CO 2 (mg Chl) −1 h −1 ]. Pyridoxal phosphate (5 m M ) inhibited starch degradation by more than 80%, but had no effect on O 2 uptake. Starch degradation rates and CO 2 evolution did not differ under acrobic and anaerobic conditions. Increasing P i in the reaction medium from 0.5 m M to 5.0 m M stimulated starch degradation by 230 and 260% under aerobic and anaerobic conditions, respectively. A rapid autooxidation of reduced ferredoxin was observed in a reconstituted system consisting of purified Chlamydomonas ferredoxin, purified Chlamydomonas NADP‐ferredoxin oxidoreductase (EC 1.6.7.1) and NADPH. Addition of isolated thylakoids from C. reinhardtii did not affect the rate of O 2 uptake. Our results clearly indicate the absence of any oxygen requirement during starch degradation in isolated chloroplasts.