The de-epoxidation of violaxanthin to antheraxanthin (Anth) and zeaxan
thin (Zeax) in the xanthophyll cycle of higher plants and the generati
on of nonphotochemical fluorescence quenching in the antenna of photos
ystem II (PSII) are induced by acidification of the thylakoid lumen. D
icyclohexylcarbodiimide (DCCD) has been shown (a) to bind to lumen-exp
osed carboxy groups of antenna proteins and (b) to inhibit the pH-depe
ndent fluorescence quenching. The possible influence of DCCD on the de
-epoxidation reactions has been investigated in isolated pea (Pisum sa
tivum L.) thylakoids. The Zeax formation was found to be slowed down i
n the presence of DCCD. The second step (Anth --> Zeax) of the reactio
n sequence seemed to be more affected than the violaxanthin --> Anth c
onversion. Comparative studies with antenna-depleted thylakoids from p
lants grown under intermittent light and with unstacked thylakoids wer
e in agreement with the assumption that binding of DCCD to antenna pro
teins is probably responsible for the retarded kinetics. Analyses of t
he DCCD-induced alterations in different antenna subcomplexes showed t
hat Zeax formation in the PSII antenna proteins was predominantly infl
uenced by DCCD, whereas Zeax formation in photosystem I was nearly una
ffected. Our data support the suggestion that DCCD binding to PSII ant
enna proteins is responsible for the observed alterations in xanthophy
ll conversion.