| RRC ID |
11287
|
| 著者 |
Rubio RO, Suzuki A, Mitsumasu K, Homma T, Niimi T, Yamashita O, Yaginuma T.
|
| タイトル |
Cloning of cDNAs encoding sorbitol dehydrogenase-2a and b, enzymatic characterization, and up-regulated expression of the genes in Bombyx mori diapause eggs exposed to 5 °C.
|
| ジャーナル |
Insect Biochem Mol Biol
|
| Abstract |
We previously cloned a cDNA for sorbitol dehydrogenase (SDH1) from Bombyx mori. In the present study we cloned two additional cDNAs encoding SDHs (designated as SDH2a and SDH2b). The amino acid sequences of SDH2ab were almost the same and had higher similarity to the SDHs of other organisms than to B. mori SDH1. The SDH2ab and SDH1genes were located in tandem within about 40 kbp on chromosome 21. SDH2ab mRNAs increased after exposing diapause eggs to 5 °C for 40 days, beginning at 2 days post-oviposition, to break diapause. However, they were at very low levels in diapausing eggs incubated at 25 °C continuously from oviposition. These changes in expression pattern of SDH2ab mRNA were almost the same as that of SDH1 mRNA. To understand whether SDH1 and SDH2 were responsible for the SDH activity seen in diapause eggs exposed to 5 °C for more than 60 days, we expressed a His-tagged SDH2a fusion protein in Escherichia coli and examined its enzymatic parameters. The maximum activity of SDH2a observed at pH 8.4∼9.0, and the Km value for sorbitol was 12.6 mM, similar to the kinetic properties of other SDHs. Due to the significantly higher similarity between SDH2a and b, they were thought to have similar kinetic properties. Therefore, we purified SDH from B. mori diapause-terminated eggs exposed to 5 °C for 300 days which showed higher SDH activity using two-step affinity chromatography. The highly purified SDH showed a higher Km value (125 mM) for sorbitol, being similar to the value (136 mM) determined previously from Eadie-Hofstee plots using egg crude extract as an enzyme source; additionally, the plots showed one slope indicating one Km value. Moreover, in silico analysis indicated that no SDH genes other than SDH1 and 2ab are present in B. mori genomic DNA. These results suggest that SDH1 activity may be responsible for the majority of the increased SDH activity seen in diapause eggs after acclimation to 5 °C rather than SDH2ab. Further, the relative sequence divergence among these genes is consistent with the idea/hypothesis that the original SDH gene was first duplicated into SDH1 and SDH2, and then SDH2 was duplicated into the SDH2a and SDH2b genes.
|
| 巻・号 |
41(6)
|
| ページ |
378-87
|
| 公開日 |
2011-6-1
|
| DOI |
10.1016/j.ibmb.2011.02.007
|
| PII |
S0965-1748(11)00056-7
|
| PMID |
21377527
|
| MeSH |
Acclimatization / genetics
Amino Acid Sequence
Animals
Base Sequence
Bombyx / enzymology*
Bombyx / genetics
Chromatography, Affinity
Cloning, Molecular
Cold Temperature
DNA, Complementary / metabolism
Escherichia coli
Female
Humans
Hydrogen-Ion Concentration
Insect Proteins / genetics
Insect Proteins / isolation & purification
Insect Proteins / metabolism*
Isoenzymes / chemistry
Isoenzymes / genetics
Isoenzymes / isolation & purification
Isoenzymes / metabolism*
Kinetics
L-Iditol 2-Dehydrogenase / genetics
L-Iditol 2-Dehydrogenase / isolation & purification
L-Iditol 2-Dehydrogenase / metabolism*
Metamorphosis, Biological / genetics
Molecular Sequence Data
Ovum / enzymology*
RNA, Messenger / analysis
Recombinant Fusion Proteins / genetics
Recombinant Fusion Proteins / metabolism*
Sequence Homology, Amino Acid
|
| IF |
3.827
|
| 引用数 |
11
|
|
WOS 分野
|
ENTOMOLOGY
BIOCHEMISTRY & MOLECULAR BIOLOGY
|
| リソース情報 |
| カイコ |
NA |
