Recombinant Expression of Hypericin Synthase Hyp1 in Escherichia coli and Elucidation of Its Solubility Mechanisms

Hypericin, the principal bioactive naphthodianthrone from Hypericum perforatum, exhibits broad‐spectrum antibacterial, antitumor, antidepressant and antiviral properties; however, its low natural abundance and suboptimal purity hinder large‐scale applications. In this study, two hypericin synthase isoforms, Hyp1A and Hyp1B, were recombinantly expressed in Escherichia coli. Following IPTG induction, Hyp1A accumulated to 94.2 μg·g-1 wet cell mass, which increased to 1.41 mg·g-1 upon fusion with a solubility‐enhancing tag. In contrast, Hyp1B achieved 7.53 mg·g-1 wet cells without modification, highlighting distinct expression phenotypes. Molecular dynamics simulations revealed that Hyp1A harbors a higher proportion of random coil and fewer α-helices relative to Hyp1B, correlating with reduced structural stability. In vitro assays confirmed that Hyp1B catalyzes emodin dimerization to hypericin, albeit with limited activity under current conditions. Collectively, these findings demonstrate the feasibility of emodin‐to‐hypericin bioconversion and establish a foundation for engineering more efficient biosynthetic processes and clinical application of hypericin.