Evolution of aldolase gene in insect and vertebrate

果糖-1，6-二磷酸糖醛缩酶是α/β桶状酶家族的成员，有A、B和C三种同工酶形式。果蝇黑腹果糖醛缩酶的三种同工酶α、β和伽马是由一个基因交替使用三个外显子4产生的。同工酶之间的性质相似。4-3和6-2的新型mRNAs也是从果蝇成虫中获得。4-3有两个最终的外显子4α和4β未拼接。从一级结构和酶学性质来看，4-3mRNA的产物为同工酶α。在黑腹葡萄球菌的组织中，编码外显子4α的信使核糖核酸的产生已知被抑制在较低的水平。我们认为编码外显子4α和4β的转录本可能产生于外显子4β的编码框架，在RNA加工过程中被识别为聚(A)信号。6-2克隆具有活性中心残基(K*Q)和FBP和FlP的活性变异，这可能为醛缩酶的分子进化提供了线索。在家蚕中发现了S和F两种醛缩酶同工酶，并对其进行了酶学和组织表达的研究。器官中5种成分的出现可能是由于S和F亚基异构体的形成。醛缩酶在内部结构上有4个同工酶特有的组序列。实验中获得的融合蛋白和果蝇醛缩酶同工酶可概括如下：(A)IGS-1和IGS-4负责确定脊椎动物醛缩酶同工酶A和C以及果蝇醛缩酶的组织特异性。在其他IGS中，IGS-4的变化可能更大。

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.