Isolation and some properties of malic enzyme from the shrimp abdomen muscle

1983 
Abstract 1. 1. Malic enzyme (EC 1.1.1.40) has been purified about 70-fold from shrimp abdomen muscle by (NH 4 ) 2 SO 4 fractionation, chromatography on DEAE-cellulose and Sephadex G-200. One band stained for enzyme activity was obtained by gel electrophoresis in the case when extract and purified malic enzyme was examined. 2. 2. The molecular weight of the native malic enzyme was determined by gel filtration to be 260,000. The isoelectric point of the isolated enzyme was at pH 4.6. 3. 3. The K m values determined at pH 7.2 for decarboxylation reaction for malate, NADP + and Mn 2+ were 0.126 mM, 16 and 3μM, respectively. The K m values for carboxylation reaction for pyruvate, NADPH and bircarbonate were 10 mM, 37 μM and 28 mM, respectively. 4. 4. The optimum pH for carboxylation reaction was at pH 7.0. The optimum pH for decarboxylation reaction was between 7.0 and 8.5 and varied with the malate concentration. The rate of pyruvate carboxylation at a pH 6.5 and 7.0 is the same as that of malate decarboxylation. 5. 5. Results obtained suggest that shrimp abdomen muscle contain only one isoenzyme of malic enzyme, the properties of which are very similar to extramitochondrial malic enzyme isolated from vertebrates.
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