Site Directed Mutagenesis to Probe for Active Site Components of Liver Mitochondrial Aldehyde Dehydrogenase
Mammalian aldehyde dehydrogenase was first purified to homogeneity in our laboratory (Feldman and Weiner, 1972a). The enzyme, isolated from horse liver, was found to be an esterase as well as a non—specific NAD—dependent dehydrogenase. At that time we did not know that the enzyme we were studying (pI=5) was from mitochondria. We found a second minor form of the enzyme with a pI=6; later it was shown that this was the cytosolic form of the enzyme. During our initial attempts to purify the mitochondrial isoenzyme we found a third form with a pI value of 4.8. It had kinetic properties identical with those of the pI 5.0 enzyme form, but it was less stable when heated at 520C. As we became more experienced with isolating the enzyme we failed to identify the low pI form. Though never proven, we felt that this was a degraded form of the mitochondrial isoenzyme.
KeywordsSite Direct Mutagenesis Aldehyde Dehydrogenase General Base Active Site Cysteine Horse Liver
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