Illustration from Scientific Research

Catalytic mechanism of PSS1. In the absence of Ca 2+ , PC binds to the catalytic site. The binding of Ca 2+ stabilizes the pocket via E197, E200 and D221. Upon l -serine binding, the side chains of E200 and H172, along with Ca 2+ , shift toward l -serine to facilitate interactions. H172 subsequently protonates l -serine, enabling the exchange of its hydroxyl group with the headgroup of the bound PC or PE molecule.

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