碩士 / 國立臺灣海洋大學 / 食品科學系 / 92 / Abstract
Malic enzyme (L-malate: NADP+-oxidooreductase(oxaloacetate decaboxylating), EC 1.1.1.40) has been purified from tilapia muscle over 1880-folds by ammonium sulfate fractionation, DE-52 ion exchange chromatography, 2’,5’ ADP-Sepharose 4B affinity chromato-graphy, and Sephacryl S-300HR gel filtration chromatography. The enzyme requires a coenzyme, NADP+, and catalyzes the decarboxylation of L-malic acid or D-malic acid. Its relative activities towards L-malic acid and D-malic acid were 100% and 6%, respectively. Molecular weight of the malic enzyme determinated by Native-PAGE method was 230 kDa. The enzyme consisted of four identical subunits with molecular weight of 56 kDa. The optimum pH for L-malic acid decarboxylation was found to be 7.8. In acidic pH, the enzyme was unstable. It’s optimum temperature was 50℃, and lost activity gradually at temperature higher than 35℃. Vmax for L-malic acid and NADP+ were 32.36、23.04 μmol NADPH/min, Km for L-malic acid and NADP+ were 0.26、0.0069 mM, respectively. The enzyme was inhibited by Zn2+、Hg2+、Al3+、Fe2+、Co2+、Cd2+. It was also inhibited by iodoacetic acid, suggesting presence of free sulfhydryl group near by the active site. Some kinds of flavonoid (rutin and morin) also inhibited malic enzyme activity.
| Identifer | oai:union.ndltd.org:TW/092NTOU5253010 |
| Date | January 2004 |
| Creators | Ya-Fu Chang, 張雅富 |
| Contributors | Pen-Hsing Tung, 童本興 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 93 |
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