Multigene families of endo-(1–4)-β-xylanases of Penicillium canescens

Abstract

Four novel genes of the enzymes of the endoxylanase (EC 3.2.1.8) families found in the mycelial fungus Penicillium canescens have been cloned. The xylB, xylC, and xylD genes encode endoxylanases of glycosyl hydrolase family 11; the xylEgene, those of family 10. In the promoter region of the xylB, xylC, and xylD genes, the binding sequences for the protein activator of xylanolytic gene transcription have been found; the promoter region of the xylB gene contains the binding sequences for the catabolite repression protein. Since the TATAA sequence, which is an element of the minimal eukaryotic promoter, has not been found in the promoter region of the xylC gene, in contrast to those of the xylB and xylD genes, it may be assumed that this gene is silent. Comparative phylogenetic analysis has shown that the cloned genes are highly homologous to some endoxylanase genes of mycelial fungi of the genera Penicillium and Aspergillus. However, within the species P. canescens, they exhibit a low homology both within and between families, and they diverge into different branches of the phylogenetic tree, which suggest divergence of the genes of this group at an early stage of evolution.