원문정보
초록
영어
A tannic acid-inducible and mycoviral-regulated laccase3 (lac3) from the chestnut blight fungus
Cryphonectria parasitica has recently been identified, but further characterization was hampered because of the precipitation of protein products by tannic acid supplementation. The present study investigated the heterologous expression of the functional laccase3 using a yeast Saccharomyces cerevisiae. Laccase activity in the culture broth of transformants measured using a laccase-specific substrate suggested that the lac3 gene was successfully expressed and the corresponding protein product secreted into the culture media. In addition, activity staining and Western blot analysis of a native gel revealed that the enzyme activity coexisted
with the protein product specific to anti-laccase3 antibody, confirming that the cloned lac3 gene is
responsible for the laccase activity. When transformants were grown on plates containing tannic acidsupplemented media, brown coloration was observed around transformed cells, indicating the oxidation of tannic acid. However, the enzymatic activity was measurable only in the selective ura- media and was negligible in nonselective YEPD culture conditions. This was in part because of the increased plasmid instability in the nonselective media. Moreover, the protein product of lac3 appears to be sensitive to the cultured YEPD broth, because a rapid decline in enzymatic activity was observed when the cultured broth of ura- media was mixed with that of YEPD. In addition, constitutive expression of the lac3 gene resulted in a reduced cell number of the lac3 transformants compared to that of mock-transformants. However, the
presence of recombinant vector without lac3 induction did not affect the growth of transformants. These results suggest that expression of the lac3 gene has an inhibitory effect on the growth of transformed S. cerevisiae and that the controlled expression of lac3 is appropriate for the possible application of recombinant yeast to the treatment of phenolic compounds.