Evolutionary genetics ofDrosophila esterases

Abstract

Over 30 carboxylester hydrolases have been identified in D. melanogaster. Most are classified as acetyl, carboxyl or cholinesterases. Sequence similarities among most of the carboxyl and all the cholinesterases so far characterised from D. melanogaster and other eukaryotes justify recognition of a carboxyl/cholinesterase multigene family. This family shows minimal sequence similarities with other esterases but crystallographic data for a few non-drosophilid enzymes show that the family shares a distinctive overall structure with some other carboxyl and aryl esterases, so they are all put in one superfamily of/beta hydrolases. Fifteen esterase genes have been mapped in D. melanogaster and twelve are clustered at two chromosomal sites. The constitution of each cluster varies across Drosophila species but two carboxyl esterases in one cluster are sufficiently conserved that their homologues can be identified among enzymes conferring insecticide resistance in other Diptera. Sequence differences between two other esterases, the EST6 carboxyl esterase and acetylcholinesterase, have been interpreted against the consensus super-secondary structure for the carboxyl/cholinesterase multigene family; their sequence differences are widely dispersed across the structure and include substantial divergence in substrate binding sites and the active site gorge. This also applies when EST6 is compared across species where differences in its expression indicate a difference in function. However, comparisons within and among species where EST6 expression is conserved show that many aspects of the predicted super-secondary structure are tightly conserved. Two notable exceptions are a pair of polymorphisms in the substrate binding site of the enzyme in D. melanogaster. These polymorphisms are associated with differences in substrate interactions in vitro and demographic data indicate that the alternative forms are not selectively equivalent in vivo.

Molecular characterization of endophytes isolated from Saccharum spp based on esterase and ribosomal DNA (ITS1-5.8S-ITS2) analyses

“…In plants, the differential expression of isoesterases have been used as a bacterial infection marker following pathogenesis (Pereira et al, 2001). However, esterase studies in vertebrates and microbes are sparse (Oakeshott et al, 1993).…”

Insecticide Resistance and Vector Control

“…Perhaps the most common resistance mechanisms in insects are modified levels or activities of esterase detoxification enzymes that metabolize (hydrolyze ester linkages) a wide range of insecticides. These esterases comprise six families of proteins belonging to the α/ß hydrolase fold superfamily (24,25). In Diptera, they occur as a gene cluster on the same chromosome (26,27).…”

Molecular weight estimation of esterase isoenzymes in closely related Drosophila Species (Diptera: Drosophilidae) in non-denaturing polyacrylamide gel electrophoresis

“…The same was postulated for EST-1 and EST-J in D. buzzatii (East et al, 1990), another member of D. repleta species group. These enzymes are classified as β-esterases, codified by the genes belonging to β-esterase cluster gene 1993). Although EST-4 and EST-5 were differently located in the insect's body and were expressed at different periods during the development, they indeed seemed to be products of the gene duplication, showing 82% identity in N-terminal amino acid sequences (Pen et al, 1986).…”

“…Several authors have recently discussed relevant aspects and mechanisms of evolution by gene duplication, including the role of selection in the process (Wagner, 2002;Zhang, 2003;Hurles, 2004). In Drosophila species, β-esterase gene cluster (Korochkin et al, 1987) is constituted by two (three in the case of D. pseudoobscura) closely linked genes, which have the same direction of transcription and similar exon/intron structure (Collet et al, 1990 (Yenikolopov et al, 1989;Brady et al, 1990;East et al, 1990;Oakeshott et al, 1990;1993). In D. pseudoobscura, β-esterase cluster gene is formed by three linked paralogous genes, Est-5C, Est-5B and Est-5A, located in X chromosome (Brady et al, 1990).…”