Examination was made of the hydrolytic activities of esterases obtained from the antennae, legs, and wings of 3-day-old cabbage looper moths,Trichoplusia ni (Hübner), by elution and by homogenation of those appendages. Pheromone hydrolysis in 1-min assays was monitored by use of tritium-labeled (Z)-7-dodecen-1-ol acetate and thin-layer chromatography to separate the reaction products. Listed according to the activities of the esterases obtained by homogenation, the organs were antennae > legs > wings. In contrast, the order according to the activities of the eluted esterases was wings > legs > antennae. Also, the eluted enzymes were less active than the esterases obtained by homogenization. The relatively high pheromone-hydrolyzing activity present in homogenized antennae suggests that the esterases originated inside the antennae and lends support to the hypothesis proposed in earlier investigations that pheromone-inactivating enzymes may play an important role in the olfactory process, possibly by clearing pheromone from the vicinity of the olfactory receptors. The esterases detected on the cuticle, on the other hand, may function by preventing surface accumulation of pheromone. The higher measured esterase activity in homogenates of prothoracic legs than of mesothoracic or metathoracic legs suggests that the prothoracic legs, which are used to clean the antennae of debris, may function by removing and degrading pheromone from the surface of antennae.
A vesicle promoting factor (VPF) in an insect cell line IAL-TNDI was partially purified from larval hemolymph of the cabbage looper, Trichoplusia ni Hubner. The polypeptide had a molecular weight estimated to be between 20.5 kD and 37.5 kD by gel permeation, 22.5 kD by the Ferguson plot on nondenaturing polyacrylamide gel electrophoresis, and 16.88 kD on sodium dodecyl sulfate PAGE. VPF fractions were isolated from hernolymph by gel permeation on FractogeP and were either subjected to chromatofocusing or preparative isoelectric focusing. After the gel permeation step, the VPF polypeptide was highly unstable during the separation and storage. The two active fractions from the isoelectric separations had isoelectric points of 6.21 and 6.36 and had specific activities of 34 and 32 vesicles/pg protein per test culture chamber. The percentage of total larval equivalent hemolymph proteins found in these fractions was less than 1%. Chromatofocusing technique also yielded an active fraction containing a single band o n nondissociating electrophoresis that had VPF activity. This band had an isoelectric point of 6.60 but had a lower specific activity of three vesicledpg protein in the VPF cell bioassay.
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