The influence of starvation on malate dehydrogenase (M DH) in rat liver was
investigated. Native electrophoresis revealed two MDH isoforms in non-star
ved rats and three isoenzymes in starved rats. After sucrose density gradie
nt centrifugation of cell organelles from liver, MDH activity was detected
in the mitochondrial and cytosolic fractions from non-starved rats. However
, additional activity was found in the peroxisomal fraction from starved ra
ts. The latter was identified as the electrophoretically new isoform in sta
rved animals. The three isoforms of malate dehydrogenase from hepatocytes w
ere separaled and partially purified by chromatography on DEAE-Toyopearl. S
everal kinetic and regulatory properties of the three isoforms were rather
similar. It is suggested that the newly expressed isoform of MDH operates i
n the glyoxylate cycle of liver peroxisomes of food-starved animals.