Subcellular distribution and characterization of human liver aldehyde dehydrogenase fractions

The subcellular distribution of human liver aldehyde dehydrogenases has been studied and the different types have been separated by ion exchange chromatography, finding evidence for slight high-K m activity in mitochondria and cytoplasmic fraction.

Abstract

The subcellular distribution of human liver aldehyde dehydrogenases (E.C. 1.2.1.3) have been studied and the different types have been separated by ion exchange chromatography. The cytoplasmic fraction contained at least two chromatographically separable aldehyde dehydrogenases, which accounted for about 30% of the total activity. One of the cytoplasmic aldehyde dehydrogenases had a high Km for aldehydes (in the millimolar range). A considerable part of the activity found in this fraction was due to an enzyme with a low Km for aldehydes (in the micromolar range). It had properties similar to those of the mitochondrial main enzyme fraction, from where it may have originated as a contamination during subcellular fractionation. Specific betaine aldehyde and formaldehyde dehydrogenases were separated from these unspecific activities in the cytoplasmic fraction. In mitochondria, where more than 50% of the total aldehyde dehydrogenase activity was found, there was also evidence for slight high-Km activity. The microsomal fraction contained only a high-Km aldehyde dehydrogenase, which accounted for about 10% of the total activity.