Stratilova_2018_World.J.Microbiol.Biotechnol_34_19

alpha-Galactosidases are assigned to the class of hydrolases and the subclass of glycoside hydrolases (GHs). They belong to six GH families and include the only characterized alpha-galactosidases from yeasts (GH 27, Saccharomyces cerevisiae). The present study focuses on an investigation of the lactose-inducible alpha-galactosidase produced by Papiliotrema flavescens. The enzyme was present on the surface of cells and in the cytosol. Its temperature optimum was about 60 degrees C and the pH optimum was 4.8; the pH stability ranged from 3.2 to 6.6. This alpha-galactosidase also exhibited transglycosylation activity. The cytosol alpha-galactosidase with a molecular weight about 110 kDa, was purified using a combination of liquid chromatography techniques. Three intramolecular peptides were determined by the partial structural analysis of the sequences of the protein isolated, using MALDI-TOF/TOF mass spectrometry. The data obtained recognized the first yeast alpha-galactosidase, which belongs to the GH 36 family. The bioinformatics analysis and homology modeling of a 210 amino acids long C-terminal sequence (derived from cDNA) confirmed the correctness of these findings. The study was also supplemented by the screening of capsular cryptococcal yeasts, which produce the surface lactose-inducible alpha- and beta-galactosidases. The production of the lactose-inducible alpha-galactosidases was not found to be a general feature within the yeast strains examined and, therefore, the existing hypothesis on the general function of this enzyme in cryptococcal capsule rearrangement cannot be confirmed.