FUSARIUM POLYCAPROLACTONE DEPOLYMERASE IS CUTINASE

Polycaprolactone (PCL), a synthetic polyester, is degraded by a variet y of microorganisms, including some phytopathogens. Many phytopathogen s secrete cutinase, a serine hydrolase that degrades cutin, the struct ural polymer of the plant cuticle. We compared wild-type strains and a cutinase-negative gene replacement mutant strain of Fusarium solani f . sp. pisi (D. J. Stahl and W. Schafer, Plant Cell 4:621-629, 1992) an d a wild-type strain of Fusarium moniliforme to show that Fusarium cut inase is a PCL depolymerase. The wild-type strains, but not the mutant strain, (i) degraded PCL and used it as a source of carbon and energy , (ii) showed induction of secreted PCL depolymerase and an esterase a ctivity of cutinase when grown in the presence of cutin, and (iii) sho wed induction of PCL depolymerase and an esterase activity of cutinase when grown in the presence of a hydrolysate of PCL, which contains PC L oligomers that are structurally similar to the natural inducers of c utinase. These results together with other details of regulation and c onditions for optimal enzyme activity indicate that the Fusarium PCL d epolymerase, required for degradation and utilization of PCL, is cutin ase.