Activation of Mitochondrial Propionyl-CoA Carboxylase.

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Abstract
The 35-55% (NH4)2SO4 fraction of the 105 000 X g supernatant of rat, beef or pork liver was found to exhibit considerable propionyl-CoA carboxylase activity in spite of the fact that the supernatant exhibited only negligible activity before fractionation. Treatment of the (NH4)2SO4 fraction with dilute acid gave a soluble preparation (S3) which increased two- to five-fold the propionyl-CoA carboxylase activity of the extract of acetone powder of rat liver mitochondria but was without effect on the same enzyme obtained from the liver supernatant. The activation was observed with the mitochondrial enzyme preparation from a normal as well as from a biotin-deficient rat, provided the latter exhibited some initial activity. S3 preparations from severely biotin-deficient rats also exhibited activation effects which were comparable to those of S3 preparations from normal animals. The activation was inhibited by avidin and the inhibition could be reversed by an excess of biotin. A similar activating effect, its inhibition by avidin, and the reversal by biotin, was observed with K+ . The potassium content of S3 preparation from normal rat or beef liver was approximately 10 [mu]mole per ml. 0.1 ml of such a preparation activated the mitochondrial propionyl-CoA carboxylase to the same extent as 1 [mu]mole of K+ per incubation mixture.