Submitted to: Journal of Helminthology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 24, 2000
Publication Date: N/A
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 that can provide the basis for development of novel control approaches. In this paper, we report the discovery of a protein-degrading enzyme within the soybean cyst nematode, a serious pest in the United States. The enzyme is associated with nematode growth and development, and may be connected to infection and feeding of this pest. This discovery is significant because it is the first report of this enzyme in any plant parasitic nematode, and the first to demonstrate a biochemical difference in this enzyme between parasitic and non-parasitic nematodes, identifying this enzyme as a potential natural target. This information will be used by researchers in the agrochemical and agricultural biotechnology industries who are developing safe, selective methods for nematode control.
Aminopeptidase activity was detected in extracts of the soybean cyst nematode, Heterodera glycines, using the synthetic substrate L-alanine -4-nitroanilide. All developmental stages examined exhibited activity, including young, maturing and old females, infective juveniles, and eggs. Activity was distributed between soluble and insoluble fractions, with the major portion of total recovered activity consistently in the insoluble portion. Substrate affinity (Km) was similar for all stages examined, ranging from 1.8 to 5.0 mM, and was similar in both soluble and insoluble fractions. Activity was solvent and heat labile, and eluted during size exclusion chromatography between 45KDa and 66KDa molecular weight markers. Aminopeptidase activity was also observed in preparations from the free-living soil nematode Caenorhabditis elegans. Kinetics were similar to H. glycines and both soluble and insoluble fractions were active. The distribution of activity between these fractions was strikingly different from H. glycines, with 90 percent of recovered activity in the soluble form.