Earthworms are common test organisms in terrestrial ecotoxicology. Continuous use of chemicals leads to loss of soil fertility and soil organisms. The susceptibility of the earthworm Lumbricus terrestrisforexposure to the commercial herbicide (Nominee) over 14 days was explored and resulting toxicological endpoints were recorded. Furthermore, earthworms were exposed to sub – lethal doses; 10.666 mg kg^-1 and 34.554 mg kg^-1of nominee for 7 days based on the EC₅₀ value, and a control was maintained.  Analysis of protein content in earthworm plasma disclosed that the whole protein content decreased in a dose/time dependent manner. Assessment of protein quality via electrophoresis of plasma proteins and analysis of amino acid profile exhibited marked changes in peptide position, number and consequently function particularly after 24 hr of exposure to lower dose meanwhile, both levels of treatment resulted in a marked suppression of protein synthesis. SDS-PAGE showed appearance of small number of peptides in case of exposure to lower dose which may be attributed to hyper-synthesis of sulfur-containing proteins with low molecular weights (<10 KDa). Exposure to nominee at tested concentrations led to a marked effect on amino acid composition and the pattern revealed the dominance of hydrophobic, acidic and basic amino acids which may reflect the nature and structure of such proteins. Isozyme analysis of earthworm protease as an essential component of humoral response, showed marked variations in isozyme number and activity between control and exposed earthworms. The inducing effect of proteases due to nominee treatment may be considered as a stress protein acts as a protective agent of earthworm cells against environmental stressors.