Development and Characteristics of the Euglena C‐Type Cytochromes*

SYNOPSIS. Two spectrally different cytochromes, referred to as cytochrome‐552 and ‐556 were isolated from Euglena gracilis (Z) grown under different environmental conditions. Their presence or absence was followed during the dark↔ light adaptation, and their concentrations calculated from spectral data. These studies indicate that cytochrome‐552 is directly dependent on chlorophyll and photosynthesis, whereas cytochrome‐556 is found in all euglenas in a constant amount, and is not dependent on photosynthesis. These cytochromes were further purified to determine differences if any in their physical‐chemical properties. The apparent molecular weight calculated from the sedimentation constants is of the order of 11,000 for cytochrome‐552, and of the order of 13,000 for cytochrome‐556. The electrophoretic mobility shows that cytochrome‐552 migrates towards the anode with a mobility depending on pH from 2.5–7.9 cm 2 /volt/sec. The oxidation‐reduction potential for cytochrome‐552 is of the order of +0.38 volts, and for cytochrome‐556 is of the order of +0.32 volts. These and the other data are compared to similar cytochromes that have been isolated from bacteria, algae, higher plants, and animal cells.