ABSTRAK Penelitian ini bertujuan untuk menentukan konsentrasi optimum penambahan enzim papain pada pakan ikan kakap putih (Lates calcarifer). Penelitian ini dilakukan di Balai Perikanan Budidaya Air Payau (BPBAP) Ujung Batee dan analisis proksimat dilakukan di Badan Riset dan Standarisasi Industri (BARISTAND) Banda Aceh pada bulan Juni hingga September 2018. Penelitian ini terdiri dari 5 taraf perlakuan dan 4 ulangan. Perlakuan yang diuji adalah perbeedaann konsentrasi enzim papain dalam pakan yaitu 0 %, 2,5 %, 5 %, 7,5 % dan 10 %. Ikan diberi pakan dua kali sehari secara ad-station (sekenyang- kenyangnya) selama 21 hari pemeliharaan. Hasil penelitian diperoleh nilai kecernaan protein berkisar antara 94,43 % - 99,98 %, kecernaan total berkisar antara 90,22 % - 99,96 %, dan nilai retensi protein berkisar antara 10,16 % - 14,59 %. Nilai tertinggi untuk kecernaan protein dan kecernaan total terdapat pada perlakuan 7,5 %, sedangkan nilai retensi tertinggi terdapat pada perlakuan 0 %. Hasil uji ANOVA menunjukkan bahwa penambahan enzim papain dalam pakan tidak berpengaruh nyata terhadap kecernaan protein, kecernaan total dan retensi protein pakan ikan kakap putih (L. calcarifer). Kata kunci : Kecernaan, retensi, papain, ikan kakap. ABSTRACT This research aimed to determine the optimum concentration of the papain enzyme addition in Seabass (Lates calcarifer) feed. This research was conducted at Brackishwater Aquaculture Center (Balai Perikanan Budidaya Air Payau – BPBAP) in Ujung Batee, meanwhile the proximate analysis was conducted at Institute for Research and Standardization of Industry (Badan Riset dan Standarisasi Industri – BARISTAND) in Banda Aceh, from June to September 2018. This research consisted of 5 steps with 4 repeatitions. Treatments included different concentrations of papain enzyme in feed, which were 0 %, 2,5 %, 5 %, 7,5 % and 10 %. The fish were fed twice a day with ad-station (as full as possible) for 21 days of treatment. The results included protein digestibility value between 94.43 % - 99.98 %, total digestibility around 90.22 % - 99.96 %, and protein retention value around 10.16 % - 14.59 %. The highest value for protein digestibility and total digestibility were obtained from the treatment with 7.5 % papain enzyme concentration. Meanwhile the highest value for retention was obtained from the treatment with 0 % papain enzyme concentration. The result of ANOVA test exhibited that the addition of papain enzyme in feed did not significantly affect the protein digestibility, total digestibility and protein retention of Seabass (L. calcarifer) feed. Keywords : Digestibility, retention, papain, Seabass.