Effects of Hydroxamic Acids Isolated from Gramineae on Adenosine 5'-triphosphate Synthesis in Chloroplasts.
Two hydroxamic acids isolated from maize extracts, 2,4-dihydroxy-7-methoxy-1,4-(2H)-benzoxazin-3(4H)-one (DIMBOA) and the 2-O-beta-d-glucopyranoside of DIMBOA, inhibit photophosphorylation by spinach chloroplasts. Both cyclic and noncyclic photophosphorylations were inhibited to the same extent. The concentrations producing 50% inhibition for DIMBOA and its glucoside were about 1 and 4 millimolar, respectively. These compounds inhibit coupled electron transport but do not affect basal or uncoupled electron transport. Both acids inhibit the ATPase activities of membrane-bound coupling factor 1 (CF(1)) and of purified CF(1). On the basis of these results, it is concluded that DIMBOA and its glucoside act as energy transfer inhibitors of photophosphorylation.
Queirolo
C B
CB
Facultad de Ciencias Básicas y Farmacéuticas, Universidad de Chile, Santiago, Casilla 653, Chile.
Andreo
C S
CS
Vallejos
R H
RH
Niemeyer
H M
HM
Corcuera
L J
LJ