Characterizaiton of cold-and high-pressure-active polygalacturonases from a deep-sea yeast, Cryptococcus liquefaciens strain N6

A deep-sea yeast, Cryptococcus liquefaciens strain N6, produces two polygalacturonases, p36 and p40 (N6PGases). These N6-PGases were highly active at 0-10 deg 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 100MPa at 24 deg C with a very small activation volume of -1.1ml/mol. At 10 deg 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 lowtemperature.