. On
the other hand, malic acid may be formed in the cytosol
by a combined activity of phosphoenolpyruvate carboxylase
(PEPC) which catalyzes carboxylation of
phosphoenolpyruvate (PEP) to produce oxalacetate that
is converted rapidly to malate by malate dehydrogenase
(MDH) and thus enter the mitochondria (Day & Copland,
1993; Wedding, 1989).