Short Communication Adaptation, Readaptation and Synthesis of Hydrogenases

Sctnedtsmus cells reach full hydrogen activity after 2.5 h of anaerobic adaptation. Exposure to oxygen inactivate * the hydrogenase immediately. Readaptation occurs with the same kinetics as primary adaptation. The fast activation and reactivation as well as the insensibility to cydoheximide suggest that hydrogenase, inactive or activated, ii present in the chloroplast all the time. The activation and even more the readaptation are sensitive to chloramphenicol. Thus, we propose that hydrogenase itself or an activating protein in the chloroplast have a rather fait turnover. Key words: Chloramphenicol — Cydoheximide — H2-photoproduction — Hydrogenase activation — Scenedesmus obliquus. Evolution of molecular hydrogen (H2-photoproduction) or its uptake upon illumination (photoreduction) have been observed widely in various groups of algae (Kessler 1974, Spruit 1962) under aerobic conditions and are considered evolutionary relics (Arnon et al. 1958, Losada et al. 1961). The enzymes catalyzing these reactions are collectively terme