Cloning, sequence analysis and overexpression of a Saccharomyces cerevisiae endopolygalacturonase-encoding gene (PGL1)

Only a few yeast strains produce pectin-degrading enzymes such as pectin esterases and depolymerases (hydrolases and lyases). Strain SCPP is the only known Saccharomyces strain to produce these pectinases. One of these pectolytic enzymes. PGL1-encoded endopolygalacturonase (EC 3.2.1.15), hydrolyses the alpha-1,4-glycosidic bonds within the rhamnogalacturonan chains in pectic substances. This paper presents the cloning and sequencing of the first S. cerevisiae gene involved in pectin degradation. Few differences were found between the two deduced amino acid sequences encoded by PGL1-1 from a pectolytic (PG+) strain (SCPP) and PGL1-2 from a non-pectolytic (PG-) strain (X2180-1B). Similarities were found with other polygalacturonases from plants and other microorganisms. Of the two S. cerevisiae genes, only the one isolated from strain SCPP was able, by overexpression, to confer endopolygalacturonase activity to a laboratory strain of S. cerevisiae. Overexpression of PGL1-1 gene in a non-pectolytic strain resulted in halo formation on polygalacturonic acid-containing agar plates stained with ruthenium red.