| Research Abstract |
Fructose-1,6-bisphoshate aldolase is a member of alpha / beta barrel enzyme family and has three types of the isozymes form : A,B and C.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. 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. The properties were similar among isozymes. The novel-type mRNAs (named, 4-3 and 6-2) was also obtained from Drosophila adult. The 4-3 has two final exons 4alpha and 4beta unspliced. The product from 4-3 mRNA was found to be isozyme alpha from the primary structure and the enzymological properties. In tissues of D.melanogaster, the production of mRNA encoding exon4alpha is known to be restrained to a low level. We concluded that the transcript-encoding exons 4alpha and 4beta, might be produced the coding frame in exon 4beta, is recognized as poly (A) signal during RNA processing. The 6-2 clone has a variant of active site residue (K*Q) and aldolase activity for FBP and FlP.This might have a clue of molecular evolution for aldolase. In Bombyx mori, two types of aldolase isozymes, S and F,were found and studied in emzymology and tissue expressions. The occurrence of five components in the organ may be due to the formation of heterotetramers of the S and F subunits.
Aldolase has four isozyme specific group sequences in internal structure. The obtained in the experiments and fusion proteins and Drosophila aldolase isozymes cab be summarised as follows : (a) IGS-1 and 4 are responsible for determining tissues-specificity of vertebrate aldolase isozyme A and C,and Drosophila aldolase. IGS-4 might be more changeable among other IGSs.
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