TY - JOUR
T1 - Oxygen activation by isolated chloroplasts from Euglena gracilis. Ferredoxin-dependent function of a fluorescent compound and photosynthetic electron transport close to photosystem I
AU - Elstner, Erich F.
AU - Wildner, Günter F.
AU - Heupel, Adelheid
PY - 1976/4
Y1 - 1976/4
N2 - Oxygen reduction by isolated chloroplast lamellae from spinach, yielding the superoxide free radical in the light, is stimulated by a fluorescent factor ("compound No. 4", isolated from Euglena gracilis strain Z) in a ferredoxin-dependent reaction. This reaction is not observed with Euglena chloroplasts, although there is a stimulation by compound No. 4 of ferredoxin-dependent oxygen reduction at the expense of NADPH + H+ as electron donor in the dark. Evidence is provided that in Euglena chloroplasts in the absence of NADP as electron acceptor a cyclic electron transport is predominating, including photosystem I, ferredoxin, NADP-ferredoxin reductase, and cytochrome552. Isolated spinach chloroplast lamellae show a similar "cyclic" electron transport after treatment with digitonin, depending on the addition of the above cofactors. This result might indicate that Euglena chloroplast lamellae show this cyclic electron transport only as an artifact due to the isolation procedure. The results furthermore indicate that the pteridine-like, fluorescent compound No. 4 is not active as the primary electron acceptor of photosystem I; it may however be involved in oxygen activation by Euglena gracilis chloroplasts.
AB - Oxygen reduction by isolated chloroplast lamellae from spinach, yielding the superoxide free radical in the light, is stimulated by a fluorescent factor ("compound No. 4", isolated from Euglena gracilis strain Z) in a ferredoxin-dependent reaction. This reaction is not observed with Euglena chloroplasts, although there is a stimulation by compound No. 4 of ferredoxin-dependent oxygen reduction at the expense of NADPH + H+ as electron donor in the dark. Evidence is provided that in Euglena chloroplasts in the absence of NADP as electron acceptor a cyclic electron transport is predominating, including photosystem I, ferredoxin, NADP-ferredoxin reductase, and cytochrome552. Isolated spinach chloroplast lamellae show a similar "cyclic" electron transport after treatment with digitonin, depending on the addition of the above cofactors. This result might indicate that Euglena chloroplast lamellae show this cyclic electron transport only as an artifact due to the isolation procedure. The results furthermore indicate that the pteridine-like, fluorescent compound No. 4 is not active as the primary electron acceptor of photosystem I; it may however be involved in oxygen activation by Euglena gracilis chloroplasts.
UR - http://www.scopus.com/inward/record.url?scp=0017067074&partnerID=8YFLogxK
U2 - 10.1016/0003-9861(76)90299-X
DO - 10.1016/0003-9861(76)90299-X
M3 - Article
C2 - 179469
AN - SCOPUS:0017067074
SN - 0003-9861
VL - 173
SP - 623
EP - 630
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -