THE CHARACTERIZATION OF A HEMOLYMPH METHYL FARNESOATE BINDING-PROTEINAND THE ASSESSMENT OF METHYL FARNESOATE METABOLISM BY THE HEMOLYMPH AND OTHER TISSUES FROM PROCAMBRUS-CLARKII

The haemolymph of Procambrus clarkii does not contain detectable level s of methyl farnesoate esterase activity. Homogenates of the hepatopan creas and the vas deferens contain significant methyl farnesoate ester ase activity which is sensitive to inhibition by diisopropylfluorophos phate. This activity may not be specific to methyl farnesoate since no nspecific esterase activity is also inhibited by diisopropylfluorophos phate. A methyl farnesoate binding protein, 93 +/- 3 kDa MW, has been identified in the haemolymph using the photoaffinity analog [H-3]FDK a nd both native and SDS-PAGE. The binding kinetics of this protein were characterized with [H-3] methyl farnesoate and the K-d for methyl far nesoate was found to be 320 +/- 150 nM.Competition experiments demonst rated that this protein has a higher affinity toward methyl farnesoate than farnesoic acid or juvenile hormone III and is therefore a methyl farnesoate binding protein.