THE PHOTOSYWTHETIC AND RESPIRATORY SYSTEMS IN EUGLENA GRACILIS 



Fulvio Perini 



INTRODUCTION 



Normal Euglena cells are unique among microaJ-gae in lacking 

 chlorophyll if grown in the dark. Dark-grown wild type cells 

 have proplastids and protochlorophyll and after exposure to light 

 form plastids and chlorophyll ^ -^^ . During the investigation of 

 this phenomenon, Nishiraiira '^ found a new cytochrome which was 

 called Euglena gracilis cytochrome 552 or c-552. This haemo- 

 protein had many properties in common i-dLth the low moleciilar 

 weight acidic c-type haemoproteins which were isolated from 

 several genera of algae hy Katoh ^-'K He postiilated the exis- 

 tence of a class of euLgal c-type cytochromes of high redox 

 potential, possibly connected with photosynthesis. Euglena 

 cytochrome c-552 was included in this class. Additional and more 

 complete work on cytochrome c-552 was carried out "by Wolken and 

 Gross '^^, who used a different approach and technique. The same 

 workers also discovered another cytochrome in dark-grown wild 

 type and mutant strains. This protein was called Euglena 

 cytochrome 556, althou^ the asymmetrical a-band has its maximum 

 at 558 W» Smlllie ^57 showed the presence of cytochrome c-552 

 In chloroplasts from Euglena , and the existence of a b-type 

 cytochrome, which he called bg, like the higher plant counterpart. 

 The result of the present Investigation confirmed most of the 

 mentioned findings. The availability of Euglena mutants blocked 

 at various stages of synthesis of the photo synthetic apparatus 

 led to the problem of differentiation between the respiratory 

 and photo synthetic electron transfer systems in this organism. 

 In addition to cytochromes c-552, b-561 (bg), 556 and a-605, 

 photo synthetic pyridine nucleotide reductase (PPNR) and flavo- 

 proteins were also foimd. 



METHOD OF PREPARATION 



Cytochromes c-552 and 55 ^ 



Light-grovm \n.ld type cells which had been washed in 0.1 N NaCl 

 + 0.05 phosphate buffer (pH 6.5) were centrifiiged at low speed. 



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