Th. Roberts et al., PLATANETIN AND 7-IODO-ACRIDONE-4-CARBOXYLIC ACID ARE NOT SPECIFIC INHIBITORS OF RESPIRATORY NAD(P)H DEHYDROGENASES IN POTATO-TUBER MITOCHONDRIA, Physiologia Plantarum, 96(2), 1996, pp. 263-267
Progress in understanding the role of NAD(P)H oxidation in plant respi
ration is restricted by the lack of access to specific inhibitors of e
ach of the unknown number of NAD(P)H dehydrogenases in the inner mitoc
hondrial membrane. Platanetin (3,5,7,8-tetrahydroxy-6-isoprenyl flavon
e) is known to be an inhibitor of external NADH oxidation by plant mit
ochondria, while 7-iodo-acridone-4-carboxylic acid (IACA) is an inhibi
tor of an internal, rotenone-insensitive NAD(P)H dehydrogenase isolate
d from yeast mitochondria. Here we show that platanetin inhibits exter
nal NAD(P)H oxidation by intact potato (Solanum tuberosum L. cv. Bintj
e) tuber mitochondria, deamino-NADH oxidation by Complex I assayed usi
ng inside-out submitochondrial particles from these mitochondria, and
rotenone-insensitive NAD(P)H oxidation by these submitochondrial parti
cles. IACA was found to inhibit the oxidation of external NADH and suc
cinate by intact mitochondria with similar efficiency. However, IACA a
lso inhibited NADPH and duroquinol oxidation by intact mitochondria as
well as deamino-NADH and NAD(P)H oxidation by inside-out submitochond
rial particles. This indicates that IACA has several sites of inhibiti
on in the electron transport chain. The lack of specificity of both pl
atanetin and IACA prevents these inhibitors from being used to shed mo
re light on the identity of the NAD(P)H dehydrogenases in plant mitoch
ondria.