Some stereochemical features of aspartate beta-decarboxylase.
Aspartate beta-decarboxylase catalyzes abortive decarboxylation/transamination of [2-3H]aspartate with at least 17% internal transfer of tritium to the pro-S position at C-4' of the resulting pyridoxamine phosphate. In the normal beta-decarboxylation reaction, at least 1.06% of the tritium from the alpha-position of aspartate appears in the product alanine. The enzyme catalyzes slow hydrogen exchange from the beta-position of alanine but not aspartate. The replacement of the beta-carboxyl group of aspartate by hydrogen occurs in an inversion mode. These results are interpreted in terms of a two-base mechanism.
D000421:Alcaligenes / Q000201:enzymology; D002250:Carbon Radioisotopes; D002262:Carboxy-Lyases / Q000378:metabolism*; D007700:Kinetics; D011865:Radioisotope Dilution Technique; D013379:Substrate Specificity; D014316:Tritium
D002250:Carbon Radioisotopes; D014316:Tritium; D002262:Carboxy-Lyases; C019747:aspartate 4-decarboxylase