J. Rasschaert et Wj. Malaisse, HEXOSE METABOLISM IN PANCREATIC-ISLETS - SUCCINATE-DEHYDROGENASE ACTIVITY IN ISLET HOMOGENATES, Cell biochemistry and function, 11(3), 1993, pp. 155-158
Succinate dehydrogenase activity was measured in rat pancreatic islet
homogenates incubated in the presence of [1,4-C-14]succinate, the reac
tion velocity being judged through the generation of (CO2)-C-14 in the
auxiliary reactions catalysed by pig heart fumarase and chicken liver
NADP-malate dehydrogenase. In the presence of 1.0 mm succinate, the r
eaction velocity averaged 5.53 +/- 0.44 pmol min-1 mug-1 islet protein
. The K(m) for succinate was close to 0.4 mm and the enzymic activity
was restricted to mitochondria. These kinetic results indicate that, u
nder the present experimental conditions, the activity of succinate de
hydrogenase does not vastly exceed that of either NAD-isocitrate dehyd
rogenase or the 2-ketoglutarate dehydrogenase complex, at least when t
he latter enzymes are activated by ADP and/or Ca2+ . Nevertheless, the
activity of succinate dehydrogenase is sufficient to account for the
increase in O2 uptake evoked in intact islets by the monomethyl ester
of succinic acid. It could become a rate-limiting step of the Krebs cy
cle in models of B-cell dysfunction.