Function
Lactamase-like protein; part of the gene cluster that mediates the biosynthesis of pestheic acid, a diphenyl ether which is a biosynthetic precursor of the unique chloropupukeananes (PubMed:24302702). The biosynthesis initiates from condensation of acetate and malonate units catalyzed by the non-reducing PKS ptaA (PubMed:24302702). As the ptaA protein is TE/CLC domain-deficient, hydrolysis and Claisen cyclization of the polyketide could be catalyzed by ptaB containing a beta-lactamase domain (PubMed:24302702). The ptaB protein might hydrolyze the thioester bond between the ACP of ptaA and the intermediate to release atrochrysone carboxylic acid, which is spontaneously dehydrated to form endocrocin anthrone (PubMed:24302702). Endocrocin anthrone is then converted to endocrocin, catalyzed by the anthrone oxygenase ptaC (PubMed:24302702). Spontaneous decarboxylation of endocrocin occurs to generate emodin (PubMed:24302702). An O-methyltransferase (ptaH or ptaI) could methylate emodin to form physcion (PubMed:24302702). PtaJ could then catalyze the oxidative cleavage of physcion, and rotation of the intermediate could then afford desmethylisosulochrin (PubMed:24302702). PtaF, a putative NADH-dependent oxidoreductase, might also participate in the oxidative cleavage step (PubMed:24302702). Desmethylisosulochrin is then transformed by another O-methyltransferase (ptaH or ptaJ) to form isosulochrin (PubMed:24302702). Chlorination of isosulochrin by ptaM in the cyclohexadienone B ring then produces chloroisosulochrin (PubMed:24302702). PtaE is responsible for the oxidative coupling reactions of both benzophenones isosulochrin and chloroisosulochrin to RES-1214-1 and pestheic acid respectively, regardless of chlorination.
Sequence
MVGKGGYRQINKALNICAFEDYLDGQQKSLPPLNDVEQISPNVLRVLGQNPGKFTLQGTNTYIIGTGEKRLLIDTGQGIPEWADLISSTLANSSIRLSAVLLSHWHGDHTGGVPDLLRLYPHLSDSIYKHSPSKGQQPIEDGQVFEVEGATVRAVHAPGHSHDHMCFVIEEENAMFTGDNVLGHGTAAVELLSTWMATLRLMQSHNCGRGYPAHGEVIPNLNAKISGELASKERRERQVLQHLNRIRKEEQGGKGSATVQRLVVEMYGDTDQQMREQALEPFIDEVLRKLAEDEKVAFQLRAGEKTWFAIALE