High-level expression of a novel protease-resistant cx-galactosidase from Thielavia terrestris

摘要

A novel alpha-galactosidase gene from Thielavia terrestris (designated TtGa127A) was cloned and expressed at high level in Pichia pastoris. The enzyme shared highest identity (40%) with glycoside hydrolase family 27 alpha-galactosidases from Penicillium purpurogenum and Penicillium simplicissimum among the characterized proteins. Extracellular expression of TtGal27 A was up to 4402.1 U/mL. TtGal27A was purified and had a specific activity of 752.0 U/mg towards p-nitrophenyl-alpha-galactopyranoside. It showed optimal pH and temperature of 4.5 and 60 degrees C, respectively, and exhibited 36.0% of its maximum activity at pH 25. The enzyme was stable within pH 3.0-9.0 and at temperatures of up to 50 degrees C after 30 min incubation. TtGa127A hydrolyzed raffinose family oligosaccharides and various galactomannans. In addition, the enzyme showed good protease resistance ( 80% of initial activity retained) towards alpha-chymotrypsin, papain, proteinase K and trypsin. These properties of TtGal27A make it potentially applicable in the food and feed industries.