Rate Response of Poly(Ethylene Terephthalate)‐Hydrolases to Substrate Crystallinity: Basis for Understanding the Lag Phase

Abstract

AbstractThe rate response of poly(ethylene terephthalate) (PET)‐hydrolases to increased substrate crystallinity (XC) of PET manifests as a rate‐lowering effect that varies significantly for different enzymes. Herein, we report the influence ofXCon the product release rate of six thermostable PET‐hydrolases. All enzyme reactions displayed a distinctive lag phase until measurable product formation occurred. The duration of the lag phase increased withXC. The recently discovered PET‐hydrolase PHL7 worked efficiently on “amorphous” PET disks (XC≈10 %), but this enzyme was extremely sensitive to increasedXC, whereas the enzymes LCCICCG, LCC, and DuraPETase had higher tolerance to increases inXCand had activity on PET disks havingXCof 24.4 %. Microscopy revealed that theXC‐tolerant hydrolases generated smooth and more uniform substrate surface erosion than PHL7 during reaction. Structural and molecular dynamics analysis of the PET‐hydrolyzing enzymes disclosed that surface electrostatics and enzyme flexibility may account for the observed differences.