Artigo
Debaryomyces hansenii UFV-1 intracellular α-Galactosidase characterization and comparative studies with the extracellular enzyme
Autor
Rezende, Sebastião T. de
Viana, Pollyanna A.
Passos, Flávia Maria Lopes
Oliveira, Jamil S.
Teixeira, Kádima N.
Santos, Alexandre M. C.
Bemquerer, Marcelo P.
Rosa, José C.
Santoro, Marcelo M.
Guimarães, Valéria M.
Institución
Resumen
Debaryomyces hansenii cells cultivated on galactose produced extracellular and intracellular α-galactosidases, which showed 54.5 and 54.8 kDa molecular mass (MALDI-TOF), 60 and 61 kDa (SDS−PAGE) and 5.15 and 4.15 pI values, respectively. The extracellular and intracellular deglycosylated forms presented 36 and 40 kDa molecular mass, with 40 and 34% carbohydrate content, respectively. The N-terminal sequences of the α-galactosidases were identical. Intracellular α-galactosidase showed smaller thermostability when compared to the extracellular enzyme. D. hansenii UFV-1 extracellular α-galactosidase presented higher kcat than the intracellular enzyme (7.16 vs 3.29 s^−1, respectively) for the p-nitrophenyl-α-d-galactopyranoside substrate. The Km for hydrolysis of pNPαGal, melibiose, stachyose, and raffinose were 0.32, 2.12, 10.8, and 32.8 mM, respectively. The intracellular enzyme was acompetitively inhibited by galactose (Ki = 0.70 mM), and it was inactivated by Cu(II) and Ag(I). Enzyme incubation with soy milk for 6 h at 55 °C reduced stachyose and raffinose amounts by 100 and 73%, respectively.