Isolation and Identification of an alpha-Galactosidase-Producing Lactosphaera pasteurii Strain and Its Enzymatic Expression Analysis

alpha-Galactosidase (EC 3.2.1.22) refers to a group of enzymes that hydrolyze oligosaccharides containing oc-galactoside-banded glycosides, such as stachyose, raffinose, and verbascose. These enzymes also possess great potential for application in sugar production, and in the feed and pharmaceutical industries. In this study, a strain of Lactosphaera pasteurii (WHPC005) that produces oc-galactosidase was identified from the soil of Western Hunan, China. It was determined that the optimal temperature and pH for this oc-galactosidase were 45 degrees C and 5.5, respectively. The activity of oc-galactosidase was inhibited by K+, Al3+, Fe3+, fructose, sucrose, lactose, galactose, SDS, EDTA, NaCl, and (NH4)(2)SO4, and enhanced by Ca2+, Fe2+, mn(2), zn(2+), glucose, and raffinose. The optimal inducer was raffinose, and the optimal induction concentration was 30 mu mol/L. The alpha-galactosidase gene was cloned using random fragment cloning methods. Sequence analysis demonstrated that the open reading frame of the alpha-galactosidase gene was 1230 bp, which encodes a putative protein of 409 amino acids in length. Bioinformatics analysis showed that the isoelectric point and molecular weight of this alpha-galactosidase were 4.84 and 47.40 kD, respectively. Random coils, alpha helixes, and beta turns were observed in its secondary structure, and conserved regions were found in the tertiary structure of this alpha-galactosidase. Therefore, this alpha-galactosidase-producing bacterial strain has the potential for application in the feed industry.