<p>The sequences in this entry belong to the superfamily of NAD-dependent epimerases and dehydratases which typically act on nucleotide-sugar substrates. The genes encoding proteins in this entry are generally in the same locus as genes involved in the biosynthesis and elaboration of hopene, the cyclization product of the polyisoprenoid squalene. This gene and its association with hopene biosynthesis in <taxon tax_id="542">Zymomonas mobilis</taxon> has been noted in the literature where the gene symbol hpnA was assigned [<cite idref="PUB00042985"/>]. Hopanoids are known to be components of the plasma membrane and to have polar sugar head groups in Z. mobilis and other species.</p>