11‐Hydroxythromboxane B2 dehydrogenase is identical to cytosolic aldehyde dehydrogenase

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Abstract
11 ‐Hydroxythromboxane B2 dehydrogenase purified from porcine kidney has been identified as cytosolic aldehyde dehydrogenase (EC 1.2.1.3). This identification is based on protein characteristics, sequence analysis of one proteolytic digest, blocked N‐terminus, subunit molecular mass of 55 kDa, and enzymatic activities. The sequence difference with the human enzyme is 7.5% in the fragments analyzed (29 exchanges of 388 positions, corresponding to the expected species variability for cytosolic aldehyde dehydrogenase The substrate thromboxane B2 contains a hemiacetal in its ring structure, but the reaction most likely proceeds via the aldehyde form of the substrate. This finding is in agreement with the proposed metabolism of 4‐hydroxycyclophosphamide and highlights the possibility that molecules containing a hemiacetal structure can function as substrates for aldehyde dehydrogenase.