Metabolism of proctolin, a pentapeptide neurotransmitter in insects |
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Authors: | G B Quistad M E Adams R M Scarborough R L Carney D A Schooley |
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Institution: | Zoecon Corporation, Agrichemical Research Department, 975 California Avenue, Palo Alto, California 94304, USA |
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Abstract: | The in vitro metabolism of tyrosyl-3, 5-3H]proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) was studied in the following tissues from the American cockroach, Periplaneta americana: proctodeum, midgut, hemolymph, brain, terminal ganglion, and coxal depressor muscles. In all tissues assayed, the Tyr-Leu bond is the primary cleavage site, but scission of the Arg-Tyr bond is also significant. Greater than 90% of the degradative activity is found in the 100,000 X g supernatant from homogenates. In vivo studies with the tobacco hornworm, Manduca sexta, show that topically applied proctolin does not penetrate larval cuticle; proctolin is readily degraded to constituent amino acids (at least to Tyr) upon ingestion. |
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