Cutinase-like biodegradable plastic-degrading enzymes from phylloplane yeasts have cutinase activity

Phylloplane yeast genera Pseudozyma and Cryptococcus secrete biodegradable plastic (BP)-degrading enzymes, termed cutinase-like enzymes (CLEs). Although CLEs contain highly conserved catalytic sites, the whole protein exhibits ≤30% amino acid sequence homology with cutinase. In this study, we analyzed whether CLEs exhibit cutinase activity. Seventeen Cryptococcus magnus strains, which degrade BP at 15 °C, were isolated from leaves and identified the DNA sequence of the CLE in one of the strains. Cutin was prepared from tomato leaves and treated with CLEs from 3 Cryptococcus species (C. magnus, Cryptococcus flavus, and Cryptococcus laurentii) and Pseudozyma antarctia (PaE). A typical cutin monomer, 10,16-dihydroxyhexadecanoic acid, was detected in extracts of the reaction solution via gas chromatography-mass spectrometry, showing that cutin was indeed degraded by CLEs. In addition to the aforementioned monomer, separation analysis via thin-layer chromatography detected high-molecular-weight products resulting from the breakdown of cutin by PaE, indicating that PaE acts as an endo-type enzyme.