To improve the capacity of using Tra fish by-products protein released from fillet Tra fish processing, study on the hydrolysis of Tra fish by-products using commercial papain was done. In order to do that, the experiment to determine V_max and K_m of the enzyme at optimal condition as pH7,5 and 55 °C was done using catfish protein as the substrate which increased the concentration from 1-30%, the amount of papain was fixed with 1 mg. From the optimal E/S ratio determined from Michalis-Menten equation, the experiment that increased the ratio E / S with a factor of 1-3 times to determine the highest concentration of catfish protein that would be hydrolyzed by the enzyme was done. Further experiment to determine the degree of hydrolysis of catfish by-products protein during 30-240 minutes was done. The degree of hydrolysis of protein hydrolysate product at 30 and 90 minute were verified by using SDS-PAGE. The results showed that when using optimal condition for papain reaction as pH 7,5 and 55^oC, V_max and K_m of enzyme reacted on Tra fish by-product protein was consequently 0,262 μmol tyrosine/minute and 0,101 g protein/10 ml. The result from the hydrolysis showed that the best pair of ratio of enzyme and substrate was 1 mg E / 2,5 g Tra fish by-product. The degree for hydrolysis after 240 minutes was 29,186% following the ratio of tyrosine born (Tyr_tp/Tyr_t) and 7,53% following OPA method. The hydrolyzed protein results which showed on SDS-PAGE proved that most of the protein hydrolyzate from Tra fish by-products were hydrolyzed well and formed in low molecular weight peptides intensity but high intensity with amino acid mixtures. The results indicated that papain can be used well for the hydrolysis of protein from Tra fish by-products. And, the product can be used as protein source feed for pigs and poultry.

Keywords: Papain, hydrolyzate, tra fish by-products,degree of hydrolysis