Abstract
The class of pyridine nucleotide-dependent -hydroxyacid oxidative decarboxylases generally catalyze the oxidative decarboxylation of a -hydroxyacid to a ketone and CO2 using NAD(Pt as the oxidant. There are two subclasses based on the metalsdependence of the reaction. Enzymes that have substrates with electron withdrawing substituents in the a- and or y-position generally do not require a metal ion cofactor, an example is 6-phosphogluconate dehydrogenase. Of the remaining enzymes, some require only a divalent metal ion; e.g. malic enzyme, while the others require both a monovalent and a divalent metal ion, for example tartate dehydrogenase.