The Putative Endoglucanase PcGH61D from Phanerochaete chrysosporium Is a Metal-Dependent Oxidative Enzyme that Cleaves Cellulose
Figure 7
Effect of PcGH61D on reduced cellulose.
Panel A displays a MALDI-TOF-MS spectrum of reduced PASC, showing peak series differing by m/z 162-repeats, typical for hexose oligosaccharides, up to m/z 4000. Note that the reduction is not complete; the close-up to the right shows that the 1177, 1339 and 1501 peaks, corresponding the reduced heptamer, octamer and nonamer, respectively, are accompanied by a peak corresponding to the native oligosaccharides with m/z -2 (two protons less). The reduced PASC (0.1%) was incubated with 40 µg/mL PcGH61D in 20mM Tris buffer pH 6.5, 1.0 mM ascorbic acid, at 50°C, and samples were taken at 90 minutes, 4 and 20 hours. The MALDI-TOF-mass spectrum of the 4 hour sample (Panel B) and clearly shows reduced products (their m/z values are indicated). The close-up to the right shows the various pentameric products (sodium adducts are marked): the DP5 lactone, m/z = 849; DP5, m/z = 851 (minor amount, not labelled); reduced DP5, m/z = 853.3; DP5ox, m/z = 867.3; sodium salt of DP5ox (-H+, +Na+), m/z = 889.2).