The Escherichia coli orthologue of the Salmonella ushB gene (ushB(c)) produces neither UDP-sugar hydrolase activity nor detectable protein, but has an identical sequence to that of Escherichia coli cdh.

Salmonella ushB, which encodes a membrane-bound UDP-sugar hydrolase, has an Escherichia coli orthologue (ushB(c)) which does not detectably produce this activity. In this report, we show that ushB(c) does not produce any detectable protein either, despite being transcribed normally. Remarkably, ushB(c) is shown to have 100% sequence identity with E. coli cdh, previously characterised as encoding an active CDP-diglyceride hydrolase, an apparent contradiction with implications regarding enzyme evolution. We suggest that a useful gene designation is cdh (ushB(c)) rather than either ushB(c) or cdh, alone.