Characterization of cold- and high-pressure-active polygalacturonases from a deep-sea yeast, Cryptococcus liquefaciens strain N6 |
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Authors: | Abe Fumiyoshi Minegishi Hiroaki Miura Takeshi Nagahama Takahiko Usami Ron Horikoshi Koki |
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Affiliation: | Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan. abef@jamstec.go.jp |
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Abstract: | A deep-sea yeast, Cryptococcus liquefaciens strain N6, produces two polygalacturonases, p36 and p40 (N6-PGases). These N6-PGases were highly active at 0-10 degrees C in comparison to a PGase from Aspergillus japonicus. The hydrolytic activity of these N6-PGases remained almost unchanged up to a hydrostatic pressure of 100 MPa at 24 degrees C with a very small activation volume of -1.1 ml/mol. At 10 degrees C, however, the activation volume increased to 3.3 or 5.4 ml/mol (p36 and p40, respectively), suggesting that the enzyme-substrate complexes can expand at their transition states. We speculate that such a volume expansion upon forming the enzyme-substrate complexes contributes to decreasing the activation energy for hydrolysis. This can account for the high activity of N6-PGases at low-temperature. |
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