Abstract
A decline in juvenile hormone (JH) titer early in the last larval instar leads to the metamorphosis of lepidopterous larvae into pupae. Clearance of JH is associated with an increase in the level of JH-specific esterase (JHE) that hydrolyzes JH into the biologically inactive JH-acid. Experiments with purified recombinant JHBP (rJHBP) and with both natural and recombinant JHE (rJHE) were designed to test the hypothesis that JHBP "protects" JH from JHE degradation in insect hemolymph. First, at low JHE concentrations, the rate of hydrolysis of JHBP-bound JH by JHE was determined by the rate of dissociation of JH from JHBP. Second, the rate of hydrolysis of JH increased with increasing JHE concentrations even in the presence of excess JHBP. In contrast, JH was not hydrolyzed by a general carboxylesterase in the presence of JHBP. Third, the rate of JH hydrolysis when the JHBP-JH complex was added to JHBP-depleted hemolymph was essentially identical to that in undiluted hemolymph. Taken together, these results suggest that JHBP protects JH from nonspecific hydrolytic processes, while still allowing highly specific JHE to hydrolyze JH by recognizing the JH-JHBP complex. Finally, JHBP efficiently extracted JH from lipophilic depots (the so-called "refractory pool", resulting in more rapid degradation of JH by JHE. Thus, JHBP is crucial for maintaining and distributing JH in hemolymph in the absence of JHE, and may assist in the rapid clearance of JH in the presence of JHE.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 727-734 |
| Number of pages | 8 |
| Journal | Insect Biochemistry and Molecular Biology |
| Volume | 25 |
| Issue number | 6 |
| DOIs | |
| State | Published - 1995 |
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Keywords
- Insect
- JH binding protein
- Metabolism
- Metamorphosis
- Protective role
ASJC Scopus subject areas
- Insect Science
- Biochemistry
- Molecular Biology
Cite this
Action of juvenile hormone (JH) esterase on the JH-JH binding protein complex. an in vitro model of JH metabolism in a caterpillar. / Touhara, Kazushige; Bonning, Bryony C.; Hammock, Bruce D.; Prestwich, Glenn D.
In: Insect Biochemistry and Molecular Biology, Vol. 25, No. 6, 1995, p. 727-734.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Action of juvenile hormone (JH) esterase on the JH-JH binding protein complex. an in vitro model of JH metabolism in a caterpillar
AU - Touhara, Kazushige
AU - Bonning, Bryony C.
AU - Hammock, Bruce D.
AU - Prestwich, Glenn D.
PY - 1995
Y1 - 1995
N2 - A decline in juvenile hormone (JH) titer early in the last larval instar leads to the metamorphosis of lepidopterous larvae into pupae. Clearance of JH is associated with an increase in the level of JH-specific esterase (JHE) that hydrolyzes JH into the biologically inactive JH-acid. Experiments with purified recombinant JHBP (rJHBP) and with both natural and recombinant JHE (rJHE) were designed to test the hypothesis that JHBP "protects" JH from JHE degradation in insect hemolymph. First, at low JHE concentrations, the rate of hydrolysis of JHBP-bound JH by JHE was determined by the rate of dissociation of JH from JHBP. Second, the rate of hydrolysis of JH increased with increasing JHE concentrations even in the presence of excess JHBP. In contrast, JH was not hydrolyzed by a general carboxylesterase in the presence of JHBP. Third, the rate of JH hydrolysis when the JHBP-JH complex was added to JHBP-depleted hemolymph was essentially identical to that in undiluted hemolymph. Taken together, these results suggest that JHBP protects JH from nonspecific hydrolytic processes, while still allowing highly specific JHE to hydrolyze JH by recognizing the JH-JHBP complex. Finally, JHBP efficiently extracted JH from lipophilic depots (the so-called "refractory pool", resulting in more rapid degradation of JH by JHE. Thus, JHBP is crucial for maintaining and distributing JH in hemolymph in the absence of JHE, and may assist in the rapid clearance of JH in the presence of JHE.
AB - A decline in juvenile hormone (JH) titer early in the last larval instar leads to the metamorphosis of lepidopterous larvae into pupae. Clearance of JH is associated with an increase in the level of JH-specific esterase (JHE) that hydrolyzes JH into the biologically inactive JH-acid. Experiments with purified recombinant JHBP (rJHBP) and with both natural and recombinant JHE (rJHE) were designed to test the hypothesis that JHBP "protects" JH from JHE degradation in insect hemolymph. First, at low JHE concentrations, the rate of hydrolysis of JHBP-bound JH by JHE was determined by the rate of dissociation of JH from JHBP. Second, the rate of hydrolysis of JH increased with increasing JHE concentrations even in the presence of excess JHBP. In contrast, JH was not hydrolyzed by a general carboxylesterase in the presence of JHBP. Third, the rate of JH hydrolysis when the JHBP-JH complex was added to JHBP-depleted hemolymph was essentially identical to that in undiluted hemolymph. Taken together, these results suggest that JHBP protects JH from nonspecific hydrolytic processes, while still allowing highly specific JHE to hydrolyze JH by recognizing the JH-JHBP complex. Finally, JHBP efficiently extracted JH from lipophilic depots (the so-called "refractory pool", resulting in more rapid degradation of JH by JHE. Thus, JHBP is crucial for maintaining and distributing JH in hemolymph in the absence of JHE, and may assist in the rapid clearance of JH in the presence of JHE.
KW - Insect
KW - JH binding protein
KW - Metabolism
KW - Metamorphosis
KW - Protective role
UR - http://www.scopus.com/inward/record.url?scp=0000736955&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0000736955&partnerID=8YFLogxK
U2 - 10.1016/0965-1748(95)00012-K
DO - 10.1016/0965-1748(95)00012-K
M3 - Article
VL - 25
SP - 727
EP - 734
JO - Insect Biochemistry and Molecular Biology
JF - Insect Biochemistry and Molecular Biology
SN - 0965-1748
IS - 6
ER -