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. The biosynthesis initiates from condensation of acetate and malonate units catalyzed by the non-reducing PKS ptaA. 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. 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. Endocrocin anthrone is then converted to endocrocin, catalyzed by the anthrone oxygenase ptaC. Spontaneous decarboxylation of endocrocin occurs to generate emodin. An O-methyltransferase (ptaH or ptaI) could methylate emodin to form physcion. PtaJ could then catalyze the oxidative cleavage of physcion, and rotation of the intermediate could then afford desmethylisosulochrin. PtaF, a putative NADH-dependent oxidoreductase, might also participate in the oxidative cleavage step. Desmethylisosulochrin is then transformed by another O-methyltransferase (ptaH or ptaI) to form isosulochrin. Chlorination of isosulochrin by ptaM in the cyclohexadienone B ring then produces chloroisosulochrin. 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