Phloroglucinol synthase is an acetyltransferase enzyme involved in the synthesis of phloroglucinol (also known as "1,3,5-trihydroxybenzene" or "cyclohexane-1,3,5-trione"), a pharmaceutically and industrially important benzentriol molecule used in medicines and explosives. The enzyme, as taken from the bacterium pseudomonas protegens (Pf-5), is a type III polyketide synthase. The enzyme cyclizes the activated form of 3,5-dioxoheptanedioate.
Phloroglucinol synthase exhibits broad substrate specificity, able to accept C4-C12 aliphatic acyl-CoAs and phenylacetyl-CoAs, yielding polyoxoalkylated alpha-pyrones by condensation with malonyl-CoA. The enzyme catalyzes the following reaction,
3 malonyl-CoA + 3 H+ = Phloroglucinol + 3 CO2 + 3 CoA
It was shown that the "k"cat for this enzyme (with malony-CoA as a substrate) was 10 min-1. Its product, phloroglucinol is used in industry as well as in the synthesis of pharmaceuticals. It can be used to make phloroglucinol but it shows low productivity.