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Molecular basis for the behavioral effects of the odorant degrading enzyme Esterase 6 in Drosophila

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ABSTRACT

Previous electrophysiological and behavioural studies implicate esterase 6 in the processing of the pheromone cis-vaccenyl acetate and various food odorants that affect aggregation and reproductive behaviours. Here we show esterase 6 has relatively high activity against many of the short-mid chain food esters, but negligible activity against cis-vaccenyl acetate. The crystal structure of esterase 6 confirms its substrate-binding site can accommodate many short-mid chain food esters but not cis-vaccenyl acetate. Immunohistochemical assays show esterase 6 is expressed in non-neuronal cells in the third antennal segment that could be accessory or epidermal cells surrounding numerous olfactory sensilla, including basiconics involved in food odorant detection. Esterase 6 is also produced in trichoid sensilla, but not in the same cell types as the cis-vaccenyl acetate binding protein LUSH. Our data support a model in which esterase 6 acts as a direct odorant degrading enzyme for many bioactive food esters, but not cis-vaccenyl acetate.

No MeSH data available.


EST6 kcat/KMEst and biological source of the most active substrates tested and other substrates of particular structural or physiological significance.Alcohol moieties are listed on the vertical and are grouped according to structural similarity. Acid moieties are listed on the horizontal. An ellipsis (…) demarcates a break in an otherwise incremental series. Data on the biological source of the substrates are taken from Supplementary Table S2. Activity results for all 87 compounds tested are given in Supplementary Table S1.
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f1: EST6 kcat/KMEst and biological source of the most active substrates tested and other substrates of particular structural or physiological significance.Alcohol moieties are listed on the vertical and are grouped according to structural similarity. Acid moieties are listed on the horizontal. An ellipsis (…) demarcates a break in an otherwise incremental series. Data on the biological source of the substrates are taken from Supplementary Table S2. Activity results for all 87 compounds tested are given in Supplementary Table S1.

Mentions: Wildtype EST6 was tested for activity against 85 bioactive ester odorants and two model substrates; 4-nitrophenyl acetate (4 NPA) and 2-naphthyl acetate (2 NA). It showed detectable activity (generally, a specificity constant kcat/KMEst > 1.5 × 104 M−1.s−1) for 47 of the bioactive esters as well as the two model substrates (Fig. 1 and Supplementary Table S1). Specificity constants for most (42) of these 49 were above 1 × 105 M−1.s−1, although none exceeded 1.3 × 106 M−1.s−1, consistent with typical kcat/KM values for enzymatic reactions in secondary metabolism25. The highest activities were seen with esters containing longer (C > 6) or more complex (branched, unsaturated or cyclic) leaving groups and acetate or propionate acid moieties, although a combination of mid-length leaving groups and acid groups (butyl decanoate) was also a relatively good substrate in these assays. The 38 compounds for which little or no activity could be detected were mainly methyl or ethyl esters or those with more complex acidic groups. cVA, which has a very long leaving group, was not hydrolysed at significant rates.


Molecular basis for the behavioral effects of the odorant degrading enzyme Esterase 6 in Drosophila
EST6 kcat/KMEst and biological source of the most active substrates tested and other substrates of particular structural or physiological significance.Alcohol moieties are listed on the vertical and are grouped according to structural similarity. Acid moieties are listed on the horizontal. An ellipsis (…) demarcates a break in an otherwise incremental series. Data on the biological source of the substrates are taken from Supplementary Table S2. Activity results for all 87 compounds tested are given in Supplementary Table S1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385555&req=5

f1: EST6 kcat/KMEst and biological source of the most active substrates tested and other substrates of particular structural or physiological significance.Alcohol moieties are listed on the vertical and are grouped according to structural similarity. Acid moieties are listed on the horizontal. An ellipsis (…) demarcates a break in an otherwise incremental series. Data on the biological source of the substrates are taken from Supplementary Table S2. Activity results for all 87 compounds tested are given in Supplementary Table S1.
Mentions: Wildtype EST6 was tested for activity against 85 bioactive ester odorants and two model substrates; 4-nitrophenyl acetate (4 NPA) and 2-naphthyl acetate (2 NA). It showed detectable activity (generally, a specificity constant kcat/KMEst > 1.5 × 104 M−1.s−1) for 47 of the bioactive esters as well as the two model substrates (Fig. 1 and Supplementary Table S1). Specificity constants for most (42) of these 49 were above 1 × 105 M−1.s−1, although none exceeded 1.3 × 106 M−1.s−1, consistent with typical kcat/KM values for enzymatic reactions in secondary metabolism25. The highest activities were seen with esters containing longer (C > 6) or more complex (branched, unsaturated or cyclic) leaving groups and acetate or propionate acid moieties, although a combination of mid-length leaving groups and acid groups (butyl decanoate) was also a relatively good substrate in these assays. The 38 compounds for which little or no activity could be detected were mainly methyl or ethyl esters or those with more complex acidic groups. cVA, which has a very long leaving group, was not hydrolysed at significant rates.

View Article: PubMed Central - PubMed

ABSTRACT

Previous electrophysiological and behavioural studies implicate esterase 6 in the processing of the pheromone cis-vaccenyl acetate and various food odorants that affect aggregation and reproductive behaviours. Here we show esterase 6 has relatively high activity against many of the short-mid chain food esters, but negligible activity against cis-vaccenyl acetate. The crystal structure of esterase 6 confirms its substrate-binding site can accommodate many short-mid chain food esters but not cis-vaccenyl acetate. Immunohistochemical assays show esterase 6 is expressed in non-neuronal cells in the third antennal segment that could be accessory or epidermal cells surrounding numerous olfactory sensilla, including basiconics involved in food odorant detection. Esterase 6 is also produced in trichoid sensilla, but not in the same cell types as the cis-vaccenyl acetate binding protein LUSH. Our data support a model in which esterase 6 acts as a direct odorant degrading enzyme for many bioactive food esters, but not cis-vaccenyl acetate.

No MeSH data available.