Sayood SF, Suh H, Wilcox CS, Schuster SM.Effect of
citreoviridin and isocitreoviridin on beef heart mitochondrial
ATPase.
Arch Biochem Biophys. 1989 May 1;270(2):714-21.
Department of Chemistry, University of Nebraska, Lincoln
68588-0304.
Citreoviridin is a toxic metabolite from fungus that has been
shown to be an inhibitor of mitochondrial F1-ATPases. Studies of
citreoviridin, however, have been compromised by the
light-dependent isomerization that it undergoes. The
isomerization is a potential source of extensive variability in
the studies, if citreoviridin and isocitreoviridin have
different kinetic effects and binding properties. Both
citreoviridin and isocitreoviridin recently have been purified
and have been shown to be stable in the dark. Using the purified
isomers, the effects of both citreoviridin and isocitreoviridin
on soluble and membrane-bound beef heart mitochondrial F1-ATPase
activity were investigated. It was found that citreoviridin was
an uncompetitive inhibitor of ATP hydrolysis, and a
non-competitive inhibitor of ITP hydrolysis catalyzed by soluble
F1-ATPase. Isocitreoviridin had no effect on the hydrolysis of
either of the triphosphates catalyzed by soluble F1-ATPase. The
inhibition constant, Ki for citreoviridin was determined as 4.5
microM for ATP hydrolysis. The inhibition constants Kii and Kis
for ITP hydrolysis were determined as 4.3 and 1.03 microM,
respectively. Citreoviridin was an uncompetitive inhibitor of
ATP hydrolysis and a noncompetitive inhibitor of ATP synthesis
catalyzed by membrane-bound F1-ATPase. The inhibition constant,
Ki, for ATP hydrolysis was around 4 microM. For ATP synthesis
the inhibition constants were determined as 0.12 and 0.16 microM
for Kis and Kii, respectively, when ADP concentration was kept
saturating. Isocitreoviridin had no effect on either activity of
the membrane-bound enzyme.
PMID: 2523213 |
