Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of the mycotoxin citrinin, a hepato-nephrotoxic compound to humans due to inhibition of respiration complex III. The pathway begins with the synthesis of a keto-aldehyde intermediate by the citrinin PKS (pksCT also named citS) from successive condensations of 4 malonyl-CoA units, presumably with a simple acetyl-CoA starter unit. Release of the keto-aldehyde intermediate is consistent with the presence of the C-terminal reductive release domain. CitA collaborates with citS by catalyzing the hydrolysis of ACP-bound acyl intermediates to free the ACP from stalled intermediates. CitB then catalyzes the oxidation of the C-12 methyl of the ketone intermediate to an alcohol intermediate which is further oxidized by the oxidoreductase citC to produce a bisaldehyde intermediate. The fourth catalytic step is catalyzed by the citD aldehyde dehydrogenase. The final transformation is the reduction of C-3 by citE to provide the chemically stable citrinin nucleus. CitE appears highly selective for its substrate as its presence in any context other than a full complement of citS and citA-D does not result in observable new compounds