Genome-wide identification,annotation and characterization of novel thermostable cytochrome P450 monooxygenases from the thermophilic biomass-degrading fungi Thielavia terrestris and Myceliophthora thermophila

Cytochrome P450 monooxygenases (P450s) are ubiquitous heme-thiolate proteins that have potential biotechnological application. Thermostable-P450s that can withstand hostile industrial conditions, such as high temperatures, extremes of pH and organic solvents, are needed for biotechnological usage. Here, for the first time, we report a large number of thermostable-P450s from two thermophilic biomass-degrading fungi, Myceliophthora thermophila and Thielavia terrestris. Genome-wide P450 analysis revealed the presence of 79 and 70 P450s (P450ome) in T. terrestris and M. thermophila. Authentic P450s containing both the P450 signature domains (EXXR and CXG) were classified as follows: T. terrestris (50 families and 56 subfamilies) and M. thermophila (49 families and 53 subfamilies). Bioinformatics analysis of P450omes suggested the presence of a large number of thermostable-P450s. Based on aliphatic index cut-off (>90), 14 and 11 P450s were determined to be thermostable in T. terrestris and M. thermophila. Among the thermostable P450s, six P450s from T. terrestris and three from M. thermophila had a melting temperature (Tm) of >65 °C, suggesting their hyperthermal tolerance. Analysis of the instability index of two ascomycete P450omes revealed the presence of 12 and 19 in vitro stable P450s in T. terrestris and M. thermophila. Overall, six P450s from T. terrestris and four from M. thermophila showed both thermal tolerance and in vitro stability. Thermophilic ascomycetes P450s are of potential interest from a structural, mechanistic and biotechnological point of view, as five P450s showed higher thermal tolerance and five showed higher in vitro stability compared to the well-characterized thermostable-P450s CYP175A1 (bacteria) and CYP119 (archaea).