Kinetic and structural evidence for the identification of 11-hydroxythromboxane B2 dehydrogenase as cytosolic...

We have recently purified 11-hydroxythromboxane B2 dehydrogenase from porcine kidney and identified it as cytosolic aldehyde dehydrogenase (EC 1.2.1.3) based on amino acid analysis and other protein characteristics. In the present paper we have studied the catalytic interaction of thromboxane B2 (TXB2) with different aldehyde substrates and a potent aldehyde dehydrogenase inhibitor, disulfiram. TXB2 was a competitive inhibitor of the aldehyde dehydrogenase reaction in assays with 3,4-dihydroxyphenylacetaldehyde, a high affinity substrate. The conversion of TXB2 to 11-dehydro-TXB2 was also inhibited by propanal and disulfiram. The protein characteristics of the enzyme have also been further studied. The native enzyme is a tetramer and has an isoelectric point of 7.0 which is comparable with that of cytosolic aldehyde dehydrogenases from other species. Taken together the present data further indicate that 11-hydroxythromboxane B2 dehydrogenase is identical with cytosolic aldehyde dehydrogenase and that substrates and inhibitors of aldehyde dehydrogenase interact with thromboxane metabolism in vitro.