Enzymatic degradation mechanism of a solution-grown poly[(R)-3-hydroxybutyrate] single crystal with an extracellular polyhydroxybutyrate depolymerase purified from Alcaligenes faecalis T1

We report the enzymatic degradation mechanism of a solution-grown poly[(R)-3-hydroxybutyrate] (P(3HB)) single crystal with an extracellular polyhydroxybutyrate depolymerase purified from Alcaligenes faecalis T1 (PhaZAfa). The P(3HB) single crystals adsorbed on highly ordered pyrolytic graphite were incubated with a wild-type or a hydrolytic-activity-disrupted mutant of PhaZAfa, and morphological changes of the single crystal before and after the incubation was observed by atomic force microscopy. We have concluded that P(3HB) single crystal has straight degradation pathway parallel to the long axis of crystal, and that PhaZAfa efficiently degrades P(3HB) polymer chain around the straight degradation pathway via three steps: adsorption, disturbance, and hydrolysis.