Enzymes are biological catalysts produced by living cells they catalyze metabolic reactions. They are soluble and colloidal substances characterized by great activity, specificity and susceptibility to the influence of environmental changes. Enzymes are the most important tools of the living cells. Cells cannot be without enzymes. They function as catalysts in a wide variety of biological reactions. Activity levels of insecticide, Quinalphos were studied in the different tissues of fresh water fish, Labeo rohita exposed to sublethal concentration (6.06 ppm) during different exposure periods of 1 day, 2 days, 3 days, 10 days and 20 days. The levels of enzymes like GOT, GPT and LDH were noticed in gill, muscle, liver and kidney, tissues with timely course of study. The fish treated with Quinalphos showed greater inhibition of enzymes during the study period.
