Divalent cations and chelators as regulators of brain fructose-1,6-bisphosphatase.
Purified fish and rat brain FruP2ase(s) are stimulated by a number of chelators, viz., histidine, EDTA, citrate, imidazole, and a number of histidine analogues. These also impart 5'-AMP sensitivity to the otherwise insensitive enzyme. Beyond 3 mM concentration, histidine inhibits the enzyme activity, which can be prevented by Mn2+. Atomic absorption spectrophotometry showed the presence of 5-6 mol of Mn2+ and Zn2+ bound to both fish and rat brain FruP2ase, which can be removed by exhaustive EDTA-dialysis. The EDTA-dialyzed brain FruP2ase records an absolute Mn2+ requirement and 5'-AMP sensitivity without any chelator treatment. The 5'-AMP sensitivity of such enzyme is abolished by prior incubation with Zn2+. The Zn(2+)-treated brain FruP2ase fails to bind to a Blue-Sepharose column, in contrast to that seen using the untreated enzyme. These results suggest that rat and fish brain FruP2ase(s) are actually Mn(2+)- and Zn(2+)-containing proteins with Zn2+ bound at or near the nucleotide-binding site.
Chattoraj-Bhattacharyya
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Department of Botany, Bose Institute, Calcutta, India.
Majumder
A L
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D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002413:Cations, Divalent / Q000032:analysis / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology*; D002951:Citrates / Q000494:pharmacology; D019343:Citric Acid; D003956:Dialysis; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D005399:Fishes; D006597:Fructose-Bisphosphatase / Q000737:chemistry / Q000187:drug effects*; D006639:Histidine / Q000031:analogs & derivatives / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008345:Manganese / Q000032:analysis / Q000494:pharmacology; D051381:Rats; D015032:Zinc / Q000032:analysis / Q000494:pharmacology
D002413:Cations, Divalent; D002614:Chelating Agents; D002951:Citrates; D007093:Imidazoles; D019343:Citric Acid; D000249:Adenosine Monophosphate; D008345:Manganese; D006639:Histidine; C029899:imidazole; D004492:Edetic Acid; D006597:Fructose-Bisphosphatase; D015032:Zinc