Depolymerization of a hydroxy fatty acid biopolymer, cutin, by an extracellular enzyme from Fusarium solani f. pisi: isolation and some properties of the enzyme

Fusarium solani f. pisi was shown to grow on the hydroxy fatty acid biopolymer cutin as the sole carbon source. Such growth conditions induced the production of an extracellular cutin depolymerising enzyme. Analysis of products enzymatically derived from labeled cutin by thin-layer chromatography and radio gas-liquid chromatography showed that the Fusarium enzyme released all classes of cutin monomers. This enzyme preparation also catalyzed hydrolysis of several model ester substrates. It did not hydrolyze triacyl glycerol and pancreatic lipase did not hydrolyze cutin, indicating that the Fusarium enzyme is not a nonspecific lipase. With p-nitrophenyl palmitate as the model substrate the enzyme showed a broad pH optimum near 8.5 and it was stimulated by Triton X-100. Maximal stimulation was obtained at 3.7 mg/ ml of the detergent. Apparent K_m for p-nitrophenyl palmitate was 1.6 × 10^?4m. p-Nitrophenyl esters of C₂–C₁₈ acids gave comparable values for K_m and V revealing no striking specificity. Treatment with diisopropyl fluorophosphate severely inhibited the enzyme while iodoacetamide and p-chloromercuric benzoate did not affect the enzymatic activity, suggesting that the Fusarium enzyme is a serine hydrolase.