The regulation of
succinyl-CoA:
acetoacetyl-CoA transferase (
CoA transferase) has been studied in 8 rat
hepatoma cell lines. Compared with normal rat hepatocytes, which have almost nondetectable activity of the
enzyme, the
hepatoma cell lines have a wide range of expression of
CoA transferase activity, from as low as 45 nmol/min/mg to as high as 960 nmol/min/mg. Western blotting showed that the different levels of
CoA transferase activity were due to differing amounts of the
enzyme in the cells. This was further attributed to the varying amounts of the
enzyme synthesized in the cells as monitored by L-[35S]
methionine labeling followed by immunoprecipitation. To study further the differential expression of
CoA transferase in the
hepatoma cell lines, the relative quantity of functional
CoA-
transferase mRNA in the cells was measured by in vitro translation. The results showed that the levels of functional
CoA transferase mRNA detected were consistent with the differences in the
enzyme activity in the cells. Since
CoA transferase is the key
enzyme responsible for the utilization of
ketone bodies as an alternative energy source, the expression of
CoA transferase in
hepatoma cells may play a role in energy production.