Submitted to: Journal of Helminthology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/30/2001
Publication Date: 3/1/2002
Citation: Masler, E. P. 2002. Aminopeptidases in Caenorhabditis elegans and Panagrellus redivivus: detection using peptide and non-peptide substrates. Journal of Helminthology 76: 45-52. 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 some of the currently used chemical nematicides from the United States within the next few years. This makes the discovery of environmentally and economically sound replacement control agents critical. One approach is to identify natural targets in nematodes that can provide the basis for development of novel control measures. To expedite this identification, the report describes the discovery of protein-degrading enzymes in two free-living nematodes. These enzymes are associated with nematode growth and development. This discovery is significant because it is now possible to identify similar enzymes in the soybean cyst nematode, a major pest of soybeans in the United States, and find fundamental biochemical differences between parasitic and non- parasitic nematode enzymes. These differences are essential to the selection of natural targets. 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: Aminopeptidase activities were detected in extracts of the free-living nematodes Caenorhabditis elegans and Panagrellus redivivus using the aminoacyl substrate L-alanine-4-nitroanilide. The activities exhibited similarities in Km (C. elegans = 2.22 mM; P. redivivus = 2.09 mM) and specific activity (C. elegans = -1.38 +/- 0.43 mAU/min/ug; P.redivivus, -1.23 +/- 0.18 mAU/min/ug). Each is inhibited competitively by amastatin (C. elegans IC50 = 0.46 uM; P. redivivus IC50 = 15.90 uM) and non-competitively by leuhistin (C. elegans IC50 = 3.00 uM; P. redivivus IC50 = 37.35 uM). The bioactive peptides adipokinetic hormone and substance P decrease the apparent aminopeptidase activities of each extract suggesting that the peptides compete with the Ala-pNA as substrates. With each extract, adipokinetic hormone appeared to be the more effective substrate. Digestion of adipokinetic hormone by C. elegans and P. redivivus extracts in the presence and absence of 1 mM amastatin produced distinct chromatographic profiles that suggest different digestion patterns for the two species. However, amastatin had clear effects on chromatographic profiles from each species indicating that an aminopeptidase is involved in the digestion of the peptide substrates. The data presented indicate that extracts of free-living nematodes are capable of metabolizing peptide hormones, and that this metabolism involves substrate-selective aminopeptidases.