Purification and Characterizationof Soluble Acid Invertase from the Hypocotyls of Mung Bean (Phaseolus radiatus L.)

녹두의 하배축에서 분리한 Soluble Acid Invertase의 정제와 특성

  • Published : 1995.09.01

Abstract

The soluble acid invertase ($\beta$-D-fructofuranoside fructohydrolase, EC 3.2.1.26) was isolated and characterized from the hypocotyls of mung bean (Phaseolus radiatus L.). The enzyme was purified to apparent homogeneity by consecutive step using diethylaminoethyl (DEAE)-cellulose anion exchange, Concanavalin (Con) A affinity and Sephacryl S-300 chromatography. The overall purification was about 148-fold with a yield of about 15%. The finally purified enzyme exhibited a specific activity of about 139 $\mu$mol of glucose produced mg-1 protein min-1 at pH 5.0 and appeared to be a single protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and nondenaturing PAGE. The enzyme had the native molecular weight of 70 kD and subunit molecular weight of 70 kD as estimated by Sephadex G-200 chromatography and SDS-PAGE, respectively, suggesting that the enzyme was composed of a monomeric protein. On the other hand, the enzyme appeared to be a glycoprotein containing N-linked high mannose oligosaccharide chain on the basis of its ability to bind to the immobilized C on A. The enzyme had a Km for sucrose of 1.8 mM at pH 5.0 and maximum activity around pH 5.0. The enzyme showed highest enzyme activity with sucrose as substrate, but the activity was slightly measured with raffinose and cellobise. No activity was measured with maltose and lactose. These results indicate the soluble acid invertase is a $\beta$-fructofuranosidase.

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