<p>Isoprenoids are a large class of compounds, with more than 20,000 structures currently known, which are found in all living organisms. Some play essential physiological roles, such as sterols that stabilise cell membranes or carotenoids involved in photosynthesis, while the function of many others is not well understood. In all eukaryotes and some prokaryotes, isoprenoids are synthesised by the mevalonate pathway, while most prokaryotes use a mevalonate-independent pathway [<cite idref="PUB00034687"/>, <cite idref="PUB00034688"/>].</p><p>This entry represents acetoacetyl-CoA synthase (<db_xref db="EC" dbkey="6.2.1.16"/>), catalysing the first step of the mevalonate pathway of isoprenoid biosynthesis via isopentenyl diphosphate.<reaction> ATP + acetoacetate + CoA = AMP + diphosphate + acetoacetyl-CoA </reaction>A Sinorhizobium protein in this entry is also required for growth on polyhydroxybutyrate, a commonly used carbon storage molecule in bacteria [<cite idref="PUB00034689"/>].</p> Acetoacetyl-CoA synthase