Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 12, 2004
Publication Date: August 8, 2004
Citation: Masler, E.P. 2004. Comparison of alanine aminopeptidase activites in Heterodera glycines and Caenorhabditis elegans. Nematology 6: 223-229.
Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack all crops of agricultural importance, causing over $10 billion in losses annually to U.S. farmers. One problem facing growers in a few years is that environmental concerns will result in the elimination of the most extensively used chemical used to kill nematodes in the United States. This makes the discovery of environmentally and economically sound replacements critical. One approach is to identify natural targets in nematodes that can provide the basis for development of novel control approaches. In this paper we report the discovery of important enzyme differences between the soybean cyst nematode, a serious pest in the United States, and a non-harmful soil nematode. The enzyme is a protein essential for nematode development, survival, feeding and reproduction. This discovery is significant because it is the first report of these enzyme characters in any plant-parasitic nematode, and the importance of the enzyme makes it a prime natural target at which to focus development of a variety of natural control strategies. This information will be used by researchers who are developing safe, selective and cutting-edge methods for nematode control.
Aminopeptidase activities in the cytosolic fraction of whole body homogenates of Caenorhabditis elegans and Heterodera glycines were examined. Activities were detected using a colorimetric assay based upon hydrolysis of aminoacyl p-nitroanilides (Xxx-pNA). Properties including substrate preference, stability and response to metal salts were evaluated. The preferred substrate for both preparations was Ala-pNA. Caenorhabditis elegans aminopeptidase activity showed much broader substrate specificity than H. glycines. In addition to Ala-pNA, Pro-pNA showed significant activity among the substrates tested with H. glycines. With C. elegans, Lys-, Met-, Arg- and Pro-pNA's (in that order) also were effective substrates. All except Pro-pNA were more active with the C. elegans preparation than with H. glycines. Pro-pNA was 3 times more active in H. glycines. Divalent cations Ca++, Mg++ and Zn++ had little effect on H. glycines activity but inhibited C. elegans activity in a dose responsive manner. Co++ was slightly (10%) inhibitory against H. glycines at 0.6-3 uM and slightly stimulatory at 6 uM. With C. elegans, Co++ was inhibitory (30%) at 1 uM with some recovery to 60% at 6 microM. Both C. elegans and H. glycines activities were inhibited by ethanol, but the rates of inhibition vs. percent alcohol were different. Methanol partially inhibited H. glycines activity (60% decrease in 15% alcohol) but increased aminopeptidase activity in C. elegans (80% increase in 15% alcohol). H. glycines activity was more stable at room temperature (97% activity after 24 hours) than C. elegans (59% activity). Addition of 0.1% bovine serum albumin increased C. elegans stability (75% at 24 hours).