Abstract
In recent years, α-galactosidase has been attracting more and more attention because of its potential applications in many aspects. Using reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends, a full-length cDNA sequence composed of 2,439 bp was cloned from Penicillium janczewskii zaleski and was subcloned into pPICZαA and transformed into Pichia pastoris strain X-33. In a 10-L fermentor, the recombinant yeast expressed α-galactosidase with a yield of 254 U/mL by methanol induction for 120 h. The recombinant enzyme showed the optimal activity at 40°C and pH 5.2. The Km values of the recombinant enzyme using p-nitrophenyl-α-D-galactopyranoside (pNPG), melibiose, raffinose and stachyose as substrates were 1, 16, 17.8 and 5.3 mM, respectively. Vmax values were 227.3, 116.7, 104.8, and 80.6 μM/min using pNPG, melibiose, raffinose and stachyose as substrates, respectively. The α-galactosidase exhibited no sensitivity to various metal ions and ethylenediaminetetraacetic acid, and hydrolyzed melibiose, raffinose and stachyose with different levels of galactose release. The biochemical characteristics of the α-galactosidase suggest that the enzyme may have a prospective application in feed industry as an additive.
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