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Feng-wen Zhang, Fu-kun Zhao, Gen-jun Xu
Molecular Cloning, Expression and Purification of Muscle Fructose-1,6-Bisphosphatase from Zaocys dhumnades: the Role of the N-Terminal Sequence in AMP Activation at Alkaline pH
An open reading frame (ORF) of snake muscle fructose 1,6-bisphosphatase (Fru-1,6-P[2]ase) was obtained by the RTPCR method with degenerate primers, followed by RACEPCR. The cDNA of Fru-1,6- P[2]ase, encoding 340 amino acids, is highly homologous to that of mammalian species, especially human muscle, with a few exceptions. Kinetic parameters of the purified recombinant enzyme, including inhibition behavior by AMP, were identical to that of the tissue form. Replacement of the Nterminal sequence of this enzyme by the corresponding region of rat liver Fru 1,6-P[2]ase shows that the activity was fully retained in the chimeric enzyme. The inhibition constant (K) of AMP at pH 7.5, however, increases sharply from 0.85M (wildtype) to 1.2mM (chimeric enzyme). AMP binding is mainly located in the Nterminal region, and the allosteric inhibition was shown not to be merely determined by the backbone of this region. The fact that the chimeric enzyme could be activated at alkaline pH by AMP indicated that the AMP activation requires the global structure beyond the area.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 381, 08/2000
Pages: 561 - 566