Depending on the type of enzyme you are looking at, these are some of the biochemical processes/methods;

Biochemical analysis

At the end of the exposure period, fish will be sacrificed by medullar transaction (Luckey, 1977) and dissected within 3 min on ice. Liver will be washed in ice cold 1.15% kcl solution, blotted dry and weighed separately. Total protein will be estimated  according to Lowry method (1951) using bovine serum albumin as a standard.

Superoxide Dismutase (SOD) Assay: Superoxide Dismutase (SOD) activity will be determined by measuring the inhibition of autoxidation of epinephrine at pH 10.2 (30 °C) as described by Magwere et al. (1997).

Catase (CAT) Assay: Catalase activity (CAT) will be determined according to the procedure of Clairborne (1995) following the absorbance of hydrogen peroxide at 240nm, pH 7.0 and 25 °C.

Reduced Glutathione (GSH) Assay: Reduced glutathione (GSH) will be determined in the 10,000 g supernatant fraction of the liver of C. gariepinus according to methods described by Jollow et al. (1974), using 5,5’-dithio-bis-2-nitrobenzoic acid (DTNB) and Tris-EDTA buffer with the absorbance being read at 412nm.

Glutathione S-Transferase (GST) Assay: Glutathione S-transferase (GST) activity will be determined by the method of Habig et al. (1974) using 1 chloro 2,4 dinitrobenzene as substrate. The reaction mixture (3 ml) contained 1.7 ml of 100 mM phosphate buffer (pH 6.5), 0.1 ml of 30 mM CDNB. After preincubating the reaction mixture at 37°C for 5 min, the reaction was started by the addition of 0.1 ml diluted sample and the absorbance was followed for 5 min at 340 nm. Reaction mixture without the enzyme was used as blank. The specific activity of glutathione S-transferase is expressed as nmoles of GSH-CDNB conjugate formed/min/mg protein using an extinction coefficient of 9.6 mM-1cm-1.

Malondialdehyde Formation (MDA) Assay: Lipid peroxidation will be determined by measuring the Thiobarbituric Acid Reacting Substances (TBARS) as described by Farombi et al. (2000). Malondialdehyde (MDA) will be quantitated by using extinction co-efficient of Σ = 1.56 × 105 M-1 cm-1 (Buege and Aust, 1978).

Liver enzymatic Assays

Alkaline Phosphatase (ALP) Assay: The activity of Alkaline phosphatase (ALP) will be measured at 410 nm in a spectrophotometer according to the method described by Alkahem  Al-Balawi et al. (2011).

Aspartate Aminotransferase (AST): AST will be determined in the 10000 g supernatant fraction using 2,4 dinitrophenyl hydrazine with the absorbance being read at 412 nm as described by (Abei, 2004).

Alanine Aminotransferase (ALT): The level of Alanine aminotransferase (ALT) will be at 413 nm using spectrophotometer as described Bergmeyer et al. (1978).