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KMID : 1160220120400030173
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Mycobiology
2012 Volume.40 No. 3 p.173 ~ p.180
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Biochemical Characterization of an Extracellular β-Glucosidase from the Fungus, Penicillium italicum, Isolated from Rotten Citrus Peel
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Park Ah-Reum
Hong Joo-Hee
Kim Jae-Jin
Yoon Jeong-Jun
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Abstract
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A β-glucosidase from Penicillium italicum was purified with a specific activity of 61.8 U/mg, using a chromatography system. The native form of the enzyme was an 88.5-kDa tetramer with a molecular mass of 354 kDa. Optimum activity was observed at pH 4.5 and 60oC, and the half-lives were 1,737, 330, 34, and 1 hr at 50, 55, 60, and 65oC, respectively. Its activity was inhibited by 47% by 5 mM Ni2+. The enzyme exhibited hydrolytic activity for p-nitrophenyl-β-D-glucopyranoside (pNP-Glu),p-nitrophenyl-β-D-cellobioside, p-nitrophenyl-β-D-xyloside, and cellobiose, however, no activity was observed for p-nitrophenyl-β-D-lactopyranoside, p-nitrophenyl-β-D-galactopyranoside, carboxymetyl cellulose, xylan, and cellulose, indicating that the enzyme was a β-glucosidase. The kcat/Km (s?1 mM?1) values for pNP-Glu and cellobiose were 15,770.4 mM and 6,361.4 mM,respectively. These values were the highest reported for β-glucosidases. Non-competitive inhibition of the enzyme by both glucose (Ki = 8.9 mM) and glucono-δ-lactone (Ki = 11.3 mM) was observed when pNP-Glu was used as the substrate. This is the first report of non-competitive inhibition of β-glucosidase by glucose and glucono-δ-lactone.
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KEYWORD
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β-Glucosidase, Cellulolytic fungi, Characterization, Identification, Purification
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