Cello-Oligosaccharide Oxidation Reveals Differences between Two Lytic Polysaccharide Monooxygenases (Family GH61) from Podospora anserina

Abstract

ABSTRACT The genome of the coprophilic ascomycete Podospora anserina encodes 33 different genes encoding copper-dependent lytic polysaccharide monooxygenases (LPMOs) from glycoside hydrolase family 61 (GH61). In this study, two of these enzymes ( P. anserina GH61A [ Pa GH61A] and Pa GH61B), which both harbored a family 1 carbohydrate binding module, were successfully produced in Pichia pastoris . Synergistic cooperation between Pa GH61A or Pa GH61B with the cellobiose dehydrogenase (CDH) of Pycnoporus cinnabarinus on cellulose resulted in the formation of oxidized and nonoxidized cello-oligosaccharides. A striking difference between Pa GH61A and Pa GH61B was observed through the identification of the products, among which were doubly and triply oxidized cellodextrins, which were released only by the combination of Pa GH61B with CDH. The mass spectrometry fragmentation patterns of these oxidized products could be consistent with oxidation at the C-6 position with a geminal diol group. The different properties of Pa GH61A and Pa GH61B and their effect on the interaction with CDH are discussed in regard to the proposed in vivo function of the CDH/GH61 enzyme system in oxidative cellulose hydrolysis.