Juvenile hormone-specific esterases in the haemolymph of the tobacco hornworm, Manduca sexta.
Juvenile hormone-specific esterases in the haemolymph of the tobacco hornworm, Manduca sexta.
复制标题
烟草天蛾（Manduca sexta）血淋巴中的保幼激素特异性酯酶。
DOI：
10.1016/0022-1910(75)90015-3
复制
发表时间：
1975
影响因子：
2.2
通讯作者：
John H. Law
中科院分区：
文献类型：
--
作者：
L. L. Sanburg;Karl J. Kramer;F. Kézdy;John H. Law
A new sensitive method for determining juvenile hormone (JH) hydrolysis has been developed which measures the release of tritiated methanol from JH labelled in the methyl ester group. Using this assay we investigated the interaction of JH with haemolymph esterases and haemolymph JH-binding protein. Haemolymph from fifth instar larvae ofManduca sextacontains two families of esterases which can be distinguished by their reactivity with diisopropylphosphorofluoridate (DFP). One group consists of general esterases which are capable of hydrolysing free JH but not JH complexed to the binding protein and are completely inhibited by low concentrations of DFP (10−4M). The other group (JH-specific esterases), relatively DFP resistant, has little detectable general esterase activity but can hydrolyse JH bound to the binding protein as well as free JH. The major JH-esterase has a sedimentation coefficient of 4·98 S and a diffusion coefficient of 6·4 × 10−7cm2sec−1. The molecular weight calculated from these values is 6·7 × 104. The general esterases are present throughout the larval stage, but the JH-specific esterases are barely detectable until the fourth day of the fifth instar when they suddenly appear at a high concentration. Since the general esterases cannot hydrolyse bound JH, one function of the binding protein is to protect JH during transport in the early instars, thus confirming that the binding protein is a true carrier of JH. In the late fifth instar prior to metamorphosis, however, JH-specific esterases appear in the haemolymph resulting in the hydrolysis of JH complexed to the carrier protein. Thus, by lowering JH titre, the JH-esterases play an important rôle in development inM. sexta.
