Subunit Structure of 
-Aminolevulinate Dehydratase from Mouse Liver
Darrell Doyle 1
From the
1 From the Department of Anatomy and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
-Aminolevulinate dehydratase purified from livers of Swiss Webster mice has a molecular weight of 250,000 by sedimentation-diffusion, gel filtration chromatography, and centrifugation in sucrose gradients. Each mole of enzyme can bind 6 moles of substrate as shown by reduction of the intermediate Schiff base with NaBH4. Denaturation with 6 m guanidine hydrochloride or sodium dodecyl sulfate in the presence of reducing agents dissociates the native enzyme into subunits of 39,500 molecular weight. No NH2-terminal amino acid can be detected after reaction with dansyl chloride. There are 14 arginine and 12 lysine residues per 39,500 g of -aminolevulinate dehydratase polypeptide. Hydrolysis with trypsin yields approximately 27 peptides, 14 of which contain arginine. All evidence is consistent with mouse liver -aminolevulinate dehydratase being composed of six identical polypeptide chains.
Alleles at the levulinate locus control the level of hepatic -aminolevulinate dehydratase by regulating the rate at which the enzyme is synthesized. Combined isotopic and immunochemical techniques reveal no differences in the subunit composition, number of active sites, or pattern of tryptic peptides between -aminolevulinate dehydratase from inbred strains of mice homozygous for different alleles at the levulinate locus. These results provide additional evidence that mutations of the levulinate locus do not affect the primary structure of hepatic -aminolevulinate dehydratase.
Submitted on March 22, 1971
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