That is, with the exception of IsPETase, the SPM calculates a path connecting loops D and W in the cases of the H/F variants (shown in red in Figure ), whereas for IsPETase, this connection is absent in both H/F and S/I variants. For the H/F variant of BurPL, the connection takes place between the W-loop trytophan (W315) and the H/F histidine (H344). In LCC and