Purification of aldehyde dehydrogenase from rat liver mitochondria by alpha-cyanocinnamate affinity chromatography

1. alpha-Cyano-4-hydroxycinnamate was coupled to Sepharose CL-4B activated with 1,2:3,4-bisepoxybutane. 2. The low-Km rat liver mitochondrial aldehyde dehydrogenase was specifically bound to this affinity medium, and could subsequently be eluted with alpha-cyano-4-hydroxycinnamate. 3. The enzyme purified in this manner had a subunit molecular mass of 55 kDa and a pI of approx. 6.5. A minor component of approx. 57 kDa was also present and had a significantly higher pI value; this may be the precursor for aldehyde dehydrogenase. 4. alpha-Cyanocinnamate and some related compounds were found to be uncompetitive inhibitors of the enzyme. 5. No cytosolic aldehyde dehydrogenase was bound to the affinity column, but a protein from a rat liver post-mitochondrial supernatant with a molecular mass of approx. 25 kDa was bound, and could be eluted subsequently with alpha-cyano-4-hydroxycinnamate.