コイ,ウナギおよびニジマス肝臓のフルクト-スビスホスファタ-ゼの特性〔英文〕

概要

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Fructose-1, 6-bisphosphatase (EC 3.1.3.11) from rainbow trout liver, eel liver, and carp he-patopancreas was purified by ammonium sulfate fractionation, followed by phosphocellulose column chromatography, and Sephadex G-200 gel filtration. Specific activity of the rainbow trout enzyme was comparable to that of the eel enzyme, while the carp enzyme was about one fifth of the above two fish species. Maximal activity of the enzyme was found around pH 7.4, irrespective of fish species. The Km values of the rainbow trout, eel and carp enzymes for FBP were 5.6, 8.2, and 12.5μM, respectively. Fish enzyme required Mg2+ for activation. In the case of carp enzyme, Mn2+ was also effective for activation. The activation constants for Mg2+ and Mn2+ ranged from 1 to 10mM and from 0.2 to 0.3mM, respectively. The activities of the rainbow trout and eel enzymes were further activated by the addition of K+ and NH4+ in the presence of Mg2+ whereas both monovalent cations inhibited carp enzyme. Na+ inhibited the activity of the fish enzyme in the presence of Mg2+. AMP stroungly inhibited the enzyme activity. In the presence of 1mM AMP and 0.5mM Mg2+ at pH 7.5, the enzymatic activity was inhibited by 57% in rainbow trout, 100% in eel, and 65% in carp.
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