Enzymology and molecular biology of bovine liver aldehyde dehydrogenases
Abstract
Aldehyde dehydrogenases (ALDH) perform important functions in the detoxication of various aldehydes, including acetaldehyde, derived from metabolism. Two closely related isozymes have been found in mammalian livers, one in cytosol and one in mitochondria. A third form exists in the microsomes. Both cytosolic and mitochondrial ALDHs were purified from bovine liver. The bovine liver ALDHs are highly analogous to the well studied enzymes isolated from horse, human, and sheep livers. Bovine mitochondrial ALDH isolated from fresh tissue was found to possess a blocked N-terminal residue. The significance of this blocked N-terminal in bovine ALDH is still unknown. As found for most mitochondrial proteins, bovine mitochondrial ALDH was initially synthesized in the cytosol as a higher molecular weight precursor. Sequence deduced from the cDNA indicates that bovine mitochondrial ALDH precursor has a 21 amino acid residue signal peptide and is able to be imported into the isolated mitochondria. The deduced sequence also shows that bovine mitochondrial ALDH has 499 amino acid residues in its mature form and shares high sequence identity (95%) to human, horse, and rat mitochondrial ALDH sequences. The three ALDHs have 500 residues. The nuclear gene coding for mitochondrial ALDH was isolated and found to span at least 25 kb. Two potential transcription initiation sites were identified. The 5$\sp\prime$-region of the gene has characteristic features typical of house-keeping genes. A G-C rich sequence was found in the 5$\sp\prime$-end region of bovine mitochondrial ALDH cDNA, analogous to what was observed in the rat cDNA. It was found, however, that in vitro bovine ALDH mRNA was translated at a much lower rate than was the rat mRNA. The translation efficiencies correlated with the stability of the predicted secondary structures of the two mRNAs.
Degree
Ph.D.
Advisors
Weiner, Purdue University.
Subject Area
Biochemistry
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