The gene encoding a cutinase homolog, LC-cutinase, was cloned from a fosmid library of a leaf-branch compost metagenome by functional screening using tributyrin agar plates. LC-cutinase shows the highest amino acid sequence identity of 59.7% to Thermomonospora curvata lipase. It also shows the 57.4% identity to Thermobifida fusca cutinase. When LCcutinase without a putative signal peptide was secreted to the periplasm of Escherichia coli cells with the assistance of the pelB leader sequence, more than 50% of the recombinant protein, termed LC-cutinase*, was excreted into the extracellular medium. It was purified and characterized. LC-cutinase* hydrolyzed various fatty acid monoesters with acyl chain lengths of 2 to 18, with a preference for short-chain substrates (C 4 substrate at most) most optimally at pH 8.5 and 50°C, but could not hydrolyze olive oil. It lost activity with half-lives of 40 min at 70°C and 7 min at 80°C. LC-cutinase* had an ability to degrade poly(-caprolactone) and polyethylene terephthalate (PET). The specific PET-degrading activity of LC-cutinase* was determined to be 12 mg/h/mg of enzyme (2.7 mg/h/kat of pNP-butyrate-degrading activity) at pH 8.0 and 50°C. This activity is higher than those of the bacterial and fungal cutinases reported thus far, suggesting that LC-cutinase* not only serves as a good model for understanding the molecular mechanism of PET-degrading enzyme but also is potentially applicable for surface modification and degradation of PET. C utinase (EC 3.1.1.74) is a lipolytic/esterolytic enzyme that hydrolyzes not only cutin, which is a major component of plant cuticle (38), but also water-soluble esters and insoluble triglycerides (12). It hydrolyzes these substrates to carboxylic acids and alcohols through the formation of an acyl enzyme intermediate, in which the active-site serine residue is acylated by the substrate. This serine residue is located within a GXSXG sequence motif and forms a catalytic triad with His and Asp. Cutinase has been found in both fungi and bacteria. The crystal structures of two fungal cutinases from Fusarium solani f. sp. pisi (22) and Glomerella cingulata (27) have been determined. According to these structures, cutinase shares a common ␣/␤ hydrolase fold with lipase and esterase (28). However, cutinase, like esterase, does not have a lid structure, which is responsible for interfacial activation of lipase (8). Therefore, cutinase does not show interfacial activation like esterase (14). Cutinase has recently received much attention because of its potential application for surface modification and degradation of aliphatic and aromatic polyesters (16), especially polyethylene terephthalate (PET), which is a synthetic aromatic polyester composed of terephthalic acid (TPA) and ethylene glycol (10,16,36,39). However, the number of cutinases, which have been studied regarding PET modification, is still limited, and this limitation may result in the delay of the research toward the practical use of cutinases. Therefore, isolation of a novel cutinase...