A constitutive flavodoxin from a eukaryotic alga

We report the isolation and some properties of a flavodoxin from a eukaryotic organism, the naturally occurring red alga $\text{Chondrus crispus}$. Unlike the situation with most other organisms the flavodoxin, under normal growth conditions, is the predominantly formed low-potential electron carrier, an accompanying ferredoxin occurring in only very small amounts. The flavodoxin is of molecular weight 21000 and one mole of FMN is present per mole of protein. Reduction of the flavoprotein proceeds via a blue flavosemiquinone radical. The flavodoxin is active both in photosynthetic NADP reduction by broken chloroplasts, and in phosphoroclastic cleavage of pyruvate by cell-free extracts of $\text{Clostridium pasteurianum}$.