THE PHOTOCONVERSION OF CHENOPODIUM CHLOROPHYLL PROTEIN

Abstract— Changes in the UV absorption spectrum with the photoconversion of Chenopodium chlorophyll protein, CP668 ⇆ CP743, and with the pH change of the CP668 and CP743 solutions, were measured. The change in the absorption spectrum of the apoprotein caused by the pH change was reversible, whereas that caused by the photoconversion was irreversible. The apoprotein may undergo a proton dissociation or association of the phenolic group in tyrosine residues upon pH change. A photooxidation in CP668 (loss of electron) caused by irradiation of CP668 solution may induce a change in the ionization state of some amino acid residues. The isoelectric points of CP668 and CP743 were determined to be 9.3 and 7.2, respectively.