Phylogenetic analysis and substrate specificity of GH2 β-mannosidases from Aspergillus species

Abstract

Phylogenetic analysis of glycoside hydrolase family 2 including Aspergillus sequences and characterised β-mannosidases from other organisms, clusters putative Aspergillus β-mannosidases in two distinct clades (A and B). Aspergillus species have at least one paralog in each of the two clades. It appears that clade A members are extracellular and clade B members intracellular. Substrate specificity analysis of MndA of Aspergillus niger (clade A) and MndB of Aspergillus nidulans (clade B) show that MndB, in contrast to MndA, does not hydrolyse polymeric mannan and has probably evolved to hydrolyse small unbranched β-mannosides like mannobiose. A 3D-model of MndB provides further insight.

Keywords: Aspergillus β-mannosidase homolog; Fine-tuned substrate specificity; Glycoside hydrolase family 2; Intracellular and extracellular β-mannosidase; Phylogenetic analysis.