Calcium activation mechanism of a noncanonical aromatic L-amino acid decarboxylase from psilocybin mushroom Psilocybe cubensis
Communications Biology – February 26, 2026
Source: OpenAlex
Summary
PcncAAAD, a unique fungal enzyme, is activated by calcium, unlike its mammalian and plant relatives. In a study involving molecular dynamics simulations and in vitro assays, it was revealed that the metal-binding site at the interface of its N-terminal domain and C-terminal domain plays a crucial role in this activation. Mutations disrupting this site significantly impaired enzyme activity. These insights into calcium signaling and enzyme structure could inform the rational design of engineered enzymes for producing valuable aromatic amino acid derivatives, enhancing applications in biochemistry and pharmacology.
Abstract
PcncAAAD is a noncanonical fungal aromatic L-amino acid decarboxylase (AAAD) featuring a unique appendage C-terminal domain (CTD) and two metal-binding sites. Unlike its mammalian and plant counterparts, PcncAAAD is activated by calcium, although the exact activation mechanism remains unclear. Here, we establish an in silico RMSD-based evaluation model through molecular dynamics simulations, validated by in vitro enzyme assays, to decipher the enzyme's calcium activation mechanism. The metal-binding site at the intra-monomer interface between the N-terminal domain and the CTD (site A) is found to play a primary role in the calcium activation of PcncAAAD, whereas the secondary site within the unique CTD (site B) contributes to the calcium-mediated stabilization of enzyme structure. Binding of calcium, but not sodium, exerts a profound influence on PcncAAAD activity by stabilizing a "lid-rim" structure underlying site A, which in turn maintains the integrity of the substrate-binding environment. In silico mutations disrupting site A or the lid-rim structure show severe structural distortion of the active site, leading to reduced or even eliminated activity as demonstrated by in vitro assays. These findings deepen our understanding of metal-activatable enzymes and hold promise for the rational design of engineered enzymes for the synthesis of aromatic amino acid derivatives.