Relative stability of recombinant versus native peroxidases from Phanerochaete chrysosporium

Two types of glycosylated peroxidases are secreted by the white-rot fungus Phanerochaete chrysosporium, lignin peroxidase (LiP) and manganese peroxida se (MnP). The thermal stabilities of recombinant LiPH2, LiPH8, and MnPH4, w hich were expressed without glycosylation in Escherichia coli, were lower t han those of corresponding native peroxidases isolated from P. chrysosporiu m. Recovery of thermally inactivated recombinant enzyme activities was high er than with that of the thermally inactivated native peroxidases; Removal of N-linked glycans from native LiPH8 and MnPH4 did not affect enzyme activ ities or thermal stabilities of the enzymes. Although LiPH2, LiPH8, and MnP H4 contained O-linked glycans, only the O-linked glycans from MnPH4 could b e removed by O-glycosidase, and the glycan-depleted MnPH4 exhibited essenti ally the same activity as nondeglycosylated MnPH4, but thermal stability de creased. Periodate-treated MnPH4 exhibited even lower thermal stability tha n O-glycosidase treated MnPH4. The role of O-linked glycans in protein stab ility was also evidenced with LiPH2 and LiPH8. Based on these data, we prop ose that neither N- nor O-linked glycans are likely to have a direct role i n enzyme activity of native LiPH2, LiPH8, and MnPH4 and that only O-linked glycans may play a crucial role in protein stability of native peroxidases. (C) 1999 Academic Press.