KINETIC AND STRUCTURAL EVIDENCE FOR THE IDENTIFICATION OF 11-HYDROXYTHROMBOXANE B-2 DEHYDROGENASE AS CYTOSOLIC ALDEHYDE DEHYDROGENASE

We have recently purified 11-hydroxythromboxane B-2 dehydrogenase from porcine kidney and identified it as cytosolic aldehyde dehydrogenase (EC 1.2.1.3) based on amino acid analysis and other protein characteri stics. In the present paper we have studied the catalytic interaction of thromboxane B-2 (TXB(2)) with different aldehyde substrates and a p otent aldehyde dehydrogenase inhibitor, disulfiram. TXB(2) was a compe titive inhibitor of the aldehyde dehydrogenase reaction in assays with 3,4-dihydroxyphenylacetaldehyde, a high affinity substrate. The conve rsion of TXB(2) to 11-dehydro-TXB(2) was also inhibited by propanal an d disulfiram. The protein characteristics of the enzyme have also been further studied. The native enzyme is a tetramer and has an isoelectr ic point of 7.0 which is comparable with that of cytosolic aldehyde de hydrogenases from other species. Taken together the present data furth er indicate that 11-hydroxythromboxane B-2 dehydrogenase is identical with cytosolic aldehyde dehydrogenase and that substrates and inhibito rs of aldehyde dehydrogenase interact with thromboxane metabolism in v itro.