Drosophila melanogaster aldolase: characterization of the isozymes alpha, beta, and gamma generated from a single gene.
Three isozymic forms, alpha, beta, and gamma, of Drosophila melanogaster aldolase are produced from a single gene by alternative usage of the triple exons 4 (4 alpha, 4 beta, and 4 gamma) [Shaw-Lee et al. (1992) J. Biol. Chem. 267, 3959-3967; Kim et al. (1992) Mol. Cell. Biol. 12, 773-783; Kai et al. (1992) J. Biochem. 112,677-688]. The expression plasmids for the respective isozymes were transfected into Escherichia coli cells, and the isozymes alpha and beta were purified to homogeneity by a simple procedure, though isozyme gamma was only partially purified. These isozymes are active towards two substrates, fructose-1,6-bisphosphate (Fru-1,6-P2) and fructose-1-phosphate (Fru-1-P), with a preference for Fru-1,6-P2 over Fru-1-P, but they have different kcat/Km values towards these two substrates; isozyme alpha shows the highest value for Fru-1,6-P2. These isozymes show similarity in optimal pHs, thermal stability, and Km values for both Fru-1,6-P2 and Fru-1-P. They are composed of four identical subunits of 40 kDa, forming a tetramer with a molecular weight of approximately 160 kDa. The three isozymes are different in primary structure only at the carboxyl-terminal region encoded by the respective exon 4. Therefore, this region should be primarily responsible for the distinct characteristics of these isozymes.
Department of Biochemistry, Saga Medical School.
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R
Zhang
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Kai
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Sugimoto
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Kusakabe
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Takasaki
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Koga
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Hori
D000595:Amino Acid Sequence; D000818:Animals; D004331:Drosophila melanogaster / Q000201:enzymology / Q000235:genetics*; D004795:Enzyme Stability; D004926:Escherichia coli; D005091:Exons; D005634:Fructose-Bisphosphate Aldolase / Q000187:drug effects* / Q000302:isolation & purification; D017344:Genes, Insect; D007527:Isoenzymes / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014714:Vertebrates / Q000235:genetics / Q000378:metabolism
D007527:Isoenzymes; D011994:Recombinant Proteins; D005634:Fructose-Bisphosphate Aldolase