Cutinases cutins

Cutinase is a hydrolytic enzyme that degrades cutin, the cuticular polymer of higher plants [4], Unlike the oflier lipolytic enzymes, such lipases and esterases, cutinase does not require interfacial activation for substrate binding and activity. Cutinases have been largely exploited for esterification and transesterification in chemical synthesis [5] and have also been applied in laundry or dishwashing detergent [6]. 

Remarkably, Brassica napus pollen was reported to have a 22 kDa cutinase that cross-reacted with antibodies prepared against F. solani f. pisi cutinase [134]. Although a 22 kDa and a 42 kDa protein that catalyzed hydrolysis of p-nitrophenyl butyrate were found in this pollen, only the former catalyzed cutin hydrolysis. Immunofluorescence microscopic examination suggested that the 22 kDa protein was located in the intine. Since the nature of the catalytic mechanism of this enzyme has not been elucidated, it is not clear whether this represents a serine hydrolase indicating that plants may have serine and thiol cutinases. The role of the pollen enzyme in controlling compatibility remains to be established. 

Conidia from pathogenic fungi that land on a plant surface carry low levels of cutinase to sense the contact with the host, and the cutin monomers generated upon contact of the conidia with the plant can be the inducers that allow the fungus to produce enough quantities of cutinase to gain access into the host (Fig. 12). This postulate was supported by many lines of evidence. Highly pa-... 

The biopolymer cutin is a major constituent of the plant cuticle that provides a protective covering for plants (1,2). At the time of infection, a number of fungal pathogens secrete an extracellular hydrolytic enzyme, cutinase, which facilitates the degradation of cutin into its constituent Ci6-to Cig-length hydroxy fatty acids (3,4). Since the enzyme is believed to... 

Acetate is known to be a good carbon source for fungi and would be expected to be the ultimate degradation product of cutin (14). The effect of acetate on the production of cutinase by the T-8 strain of F. solani was examined and compared with that of glucose. Since previous studies showed that hydrolysis of the artificial substrate p-nitrophenylbutyrate, PNB, was specifically hydrolyzed by cutinase in the T-8 strain, this activity was used to measure cutinase levels (8). Figure 1 illustrates that basal levels of cutinase activity were detected in the growth medium when T-8 was grown on... 

Figure 2. Specific activity of cutinase resulting from growth in cutin-containing medium with the addition of a second carbon source. The T-8 strain of F. solani was grown on medium containing 200 mg of apple cutin and glucose (A) or acetate (B). (Reproduced with permission from Ref. 13. 1986, American Society for Microbiology.)...

Next the parent and mutant were compared for their ability to induce cutinase by cutin and hydrolyzed cutin (consisting of small molecular weight inducers) after growth on glucose. As shown in Figure 5, cutinase activity increased over the three-day induction period for both strains in the presence of cutin (Panel A) or hydrolyzed cutin (Panel B) however, cutinase was induced less effectively in the mutant strain, as evidenced by an 80-90% reduction. Hydrolyzed cutin was a 10-fold less effective inducer than cutin in both strains. These data indicated that lack of induction in the mutant was not related to its inability to hydrolyze cutin to small molecular weight inducers. Consequently the defect observed was not related to the inability of the mutant to produce the inducer. 

The PNB-1 mutant is a leaky mutant that is partially defective in cutinase production, and apparently produced 80 to 90% less normal enzyme. The regulation of the residual enzyme in the mutant was unchanged. The enzyme was repressed by glucose, and was induced by cutin or hydrolyzed cutin after depletion of glucose. Cutinase activity increased over a 15-day time period when the mutant was grown on cutin as the sole carbon source. The mutant was also less virulent than the parental strain. The nature of the PNB-1 mutation remains to be elucidated and... 

Lin TS, Kolattukudy PE (1978) Induction of a biopolyester hydrolase (cutinase) by low levels of cutin monomers in Fusarium solani f sp. pisi. J Bacteriol 133 942-951... 

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