Induction of a peroxisomal malate dehydrogenase isoform in liver of starved rats

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.