Submitted to: Journal of Helminthology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/20/2002
Publication Date: 3/1/2003
Citation: Masler, E. P. 2003. In vitro metabolism of an insect neuropeptide by homogenates of the nematode Caenorhabditis elegans. Journal of Helminthology 77: 43-48. Interpretive Summary: Plant-parasitic nematodes attack all crops of agricultural importance, causing over $10 billion in losses annually to U.S. farmers. One problem facing growers is that environmental concerns will result in the elimination of the most extensively used chemical nematicide from the United States within the next few years. This loss makes the discovery of environmentally and economically sound replacement control agents critical. One approach for such discovery is to identify natural targets in nematodes that can provide the biochemical basis for development of novel control measures. To expedite this identification, this report describes the discovery of a hormone-degrading system in a non-parasitic nematode. This system has enzymes which destroy a hormone that controls fat levels. This discovery is significant because it will make it possible to identify similar systems in plant-parasitic nematodes, and find fundamental biochemical differences between parasitic and non-parasitic nematode enzymes. These differences are essential to the selection of natural targets that will discriminate between parasitic and beneficial nematodes. This information will be used by researchers in the agrochemical and agricultural biotechnology industries who are developing safe, selective methods for nematode control.
Technical Abstract: The cytosolic fraction of homogenates from the free-living soil nematode Caenorhabditis elegans is capable of metabolizing the insect neuropeptide adipokinetic hormone, a decapeptide blocked at the N-terminus by a pGlu residue. Analysis of digests by RP-HPLC and LC-MS revealed that an initial endoproteolytic cleavage step produced a heptapeptide with an unblocked N- terminus that can serve as a substrate for aminopeptidases. The aminopeptidase activity is depressed in the presence of the inhibitor amastatin; the initial product of the endoproteolytic step accumulates during incubation, and expected aminopeptidase product peptides are reduced in amount, as assessed by chromatographic peak size. The absence of some expected peptide fragments in the reaction mixtures suggests that multiple proteases contribute to short peptide half-lives. Comparison of the adipokinetic hormone digestion in C. elegans to that reported previously for insects reveals the same general pattern of peptide fragment production.