336 JAMES H. C, SMITH 



with the pK values of various amino acids suggests the participation of 

 lysine, cysteine, and tyrosine. Changes in ultraviolet absorption of the 

 holochrome with pH implicates cysteine and tyrosine. Furthermore, the 

 limited transformation produced by ultraviolet radiation points strongly 



Chlorella Vulgaris 

 Mutant 60 



pH =1133 

 55 min 



pH = ll-54 

 2 _ 135 m in 



pH=ll-56 

 2 25 min 



400 450 500 550 600 650 700 750 

 Wavelength (m/x) 



Fig. 8. The effects on the absorption spectrum and transformation of the 

 protochlorophyll holochrome caused by extended treatment at high pH. 



to tyrosine as binding from 25 to 30",, of the protochlorophyll. The shift 

 of the absorption spectrum of protochlorophyll holochrome in the visible 

 with increased pH values also implies a disturbance of the linkage between 

 pigment and protein. pH values of 11 and above cause rapid splitting of the 

 cyclopentanone ring. How far this controls the inhibition of transformation 

 is yet to be determined. 



References 



1. Smith, J. H. C, and Kupke, D. W., Nature, Loud. 178, 751-752 (1956). 



2. Smith, J. H. C, and Coomber, J., Yearb. Carneg. lustu. 58, 333 (1959). 



3. Smith, J. H. C, Yearb. Carneg. Instil. 57, 289 (1958). 



4. Goodwin, T. W., and Phagpolngarm, S., Biochem. jf. 76, 197-199 (i960). 



