Aminopeptidase-like activities in Caenorhabditis elegans and the soybean cyst nematode, Heterodera glycines

Abstract

Aminopeptidase-like activities in crude whole body extracts of the free-living nematode Caenorhabditis elegans and the plant parasitic soybean cyst nematode Heterodera glycines were examined. General characteristics including pH optima, heat lability, and inactivation of enzyme by organic solvent were the same for the two species. All developmental stages of H. glycines exhibited activity. In older females, activity was present primarily in the eggs. Affinity for the substrate L-alanine-4-nitroanilide was the same regardless of the stage examined, and was similar for the two species (Km=2.3±0.3 mM FOR C. ELEGANS AND 2.9±0.2 Mm for H. glycines). Nearly all (>95%) of C. elegans aminopeptidase-like activity was present in the soluble fraction of the extract, while H. glycines activity was distributed between the soluble and membrane fractions. Specific activities of the soluble enzymes were highest in C. elegans and H. glycines juveniles. The C. elegans enzyme was susceptible to a number of aminopeptidase inhibitors, particularly to amastatin and leuhistin, each of which inhibited aminopeptidase-like activity more than 90% at 90 μm. In H. glycines, aminopeptidase-like activity was inhibited 39% by amastatin at 900 μm. The apparent molecular weight of the soluble C. elegans enzyme is 70–80 kDa. Some activity in H. glycines is present in the 70–80 kDa range, but most activity (80–90%) is associated with a very high molecular weight (>240 kDa) component.