Molecular characterization and functional analysis of novel carboxyl/cholinesterases with GQSAG motif in the silkworm Bombyx mori.
We have previously cloned and characterized BmJHE, a juvenile hormone (JH)-selective esterase (JHE) that is important for JH titer regulation in the silkworm Bombyx mori. Here, we sought to determine whether multiple genes might function as JH-specific esterase in this species. We searched for putative carboxyl/cholinesterase (CCE) genes having GQSAG, a highly conserved motif in JHE, by the use of silkworm genomic database. Five novel CCE genes (Bmcce-1-5) were identified and their cDNA sequences and intron-exon structures were determined. We investigated the developmental expression patterns of these CCE genes by real-time quantitative PCR analysis and found that their expression patterns varied among developmental stages and organs. Of the proteins produced by the five genes, only BmCCE-5 had the ability to degrade JH; however, this protein might not function as a JH-specific esterase in vivo as it had a high K(m) value for JH. On the other hand, BmCCE-5 degraded general esterase substrates efficiently. Since Bmcce-5 was strongly expressed in Malpighian tubules and the gut, it might function in digestion or xenobiotic metabolism. Our results suggest that of the CCEs containing a GQSAG motif only BmJHE can function as a JH-specific degradation enzyme in the silkworm.
Tsubota
Takuya
T
National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
Shimomura
Masaru
M
Ogura
Takehiko
T
Seino
Atsushi
A
Nakakura
Takayo
T
Mita
Kazuei
K
Shinoda
Tetsuro
T
Shiotsuki
Takahiro
T
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000201:enzymology*; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002802:Cholinesterases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D017931:DNA Primers; D005091:Exons; D007438:Introns; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D002265:Carboxylic Ester Hydrolases; D002802:Cholinesterases