ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
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 O2 (mg Chl)−1 h−1 consumed. 1 000 nmol glucose (mg Chl)−1h−1 degraded]. Evolution of CO2 under aerobic conditions [9.8–28 nmol (mg Chl)−1 h−1] was stimulated by addition of 0.1–0.5 mM oxaloacetate [393–425 nmol CO2 (mg Chl)−1 h−1]. Pyridoxal phosphate (5 mM) inhibited starch degradation by more than 80%, but had no effect on O2 uptake. Starch degradation rates and CO2 evolution did not differ under acrobic and anaerobic conditions. Increasing Pi in the reaction medium from 0.5 mM to 5.0 mM 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 O2 uptake. Our results clearly indicate the absence of any oxygen requirement during starch degradation in isolated chloroplasts.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1989.tb02071.x
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