V. Scheumann et al., Chlorophyll a formation in the chlorophyll b reductase reaction requires reduced ferredoxin, J BIOL CHEM, 273(52), 1998, pp. 35102-35108
The reduction of chlorophyllide b and its analogue zinc pheophorbide b in e
tioplasts of barley (Hordeum vulgare L.) was investigated in detail. In int
act etioplasts, the reduction proceeds to chlorophyllide a and zinc pheopho
rbide a or, if incubated together with phytyldiphosphate, to chlorophyll a
and zinc pheophytin a, respectively. In lysed etioplasts supplied with NADP
H, the reduction stops at the intermediate step of 7(1)-OH-chlorophyll(ide)
and Zn-7(1)-OH-pheophorbide or Zn-7(1)OH-pheophytin. However, the final re
duction is achieved when reduced ferredoxin is added to the lysed etioplast
s, suggesting that ferredoxin is the natural cofactor for reduction of chlo
rophyll b to chlorophyll a. The reduction to chlorophyll a requires ATP in
intact etioplasts but not in lysed etioplasts when reduced ferredoxin is su
pplied. The role of ATP and the significance of two cofactors for the two s
teps of reduction are discussed.