Adenosylcobalamin dependent diol dehydrase

Protein-chemical Properties of Apoenzyme. Adenosylcobalamin-dependent diol dehydrase was discovered and isolated first by Abeles and co-workers (3, 4) in the cells of Klebsiella pneumoniae (formerly known as Aerohacter aero genes) ATCC 8724 grown without aeration in a glycerol or glycerol-1,2-propanediol medium. This enzyme catalyzes the conversion of 1,2-propanediol, 1,2-ethanediol, and glycerol to propionaldehyde, acetaldehyde, and j3-hydroxypropionaldehyde, respectively (4, 5). Adenosylcobalamin and K+ or other monovalent cations of a similar size are required for catalysis. Recently, the au-... 

Tobimatsu T, Hara T, Sakaguchi M, Kishimoto Y, Wada Y, Isoda M, Sal T, Toraya T (1995) Molecular cloning, sequencing, and expression of the genes encoding adenosylcobalamin-dependent diol dehydrase of Klebsiella oxytoca. J Biol Chem 270 712-7148... 

Interaction with Adenosylcobalamin. It has been considered generally that adenosylcobalamin or its analogs binds to the apoprotein of diol dehydrase or other adenosylcobalamin-dependent enzymes almost irreversibly (4). However, we found that the holo-enzyme of diol dehydrase was resolved completely into intact apoen-zyme and adenosylcobalamin when subjected to gel filtration on a Sephadex G-25 column in the absence of K+ (9, 10). Among the inactive complexes of diol dehydrase with irreversible cobalamin inhibitors, those with cyanocobalamin and methylcobalamin also were resolved upon gel filtration on Sephadex G-25 in the absence of both K+ and substrate, yielding the apoenzyme, which was reconstitutable into the active holoenzyme (II). The enzyme-hydroxocobalamin complex, however, was not resolvable under the same conditions. The enzyme-cobalamin complexes were not resolved at all by gel filtration in the presence of both K+ and substrate. When gel filtration of the holoenzyme was carried out in the presence of K+ only, the holoen-... 

FIGURE 4. The eleven adenosylcobalamin-dependent rearrangements so far described. Notes D-a-lysine [L-p-lysine] 5,6-aminomutase catalyzes similar rearrangements on two substrates diol dehydrase and glycerol dehydrase have over-lapping substrate specificity. 

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