author(s)
Md. Abdur Rashid* and Dilshad Tamanna Rahman

abstract
Esterase isozymes of Clarias batrachus and C. gariepinus were studied on 7.5% Polyacrilamide Gel Electrophoresis (PAGE) stained with a and b naphthyl acetates as substrates to see the tissue specific variation of this enzyme from nineteen different tissues. Maximum six esterase bands (Est-11.52±0.01, Est-21.26±0.01, Est-30.99±0.01, Est-40.67±0.02, Est-50.33±0.01 and Est-60.17±0.02) were observed in Asian catfish (C. batrachus) where as African catfish (C. gariepinus) shown only four (Est-11.43±0.02, Est-21.22±0.03, Est-31.02±0.02 and Est-50.33±0.02). Localization of esterase isozymes were observed in different tissues of both Asian and African catfishes that indicated the switch on and off of specific allele based on the physio-chemical condition of corresponding tissues. Relatively higher concentration of esterase isozymes were found in digestive tissues. High number of esterase bands was found in Asian catfish which seems to indicate the higher allelic variation than in African catfish.