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Jamur merang adalah komoditi pangan yang mempunyai nilai gizi cukup baik dan mulai dibudidayakan di daerah Jawa Tengah. Masalah yang cukup merugikan adalah cepatnya jamur merang menjadi coklat. Salah satu penyehab terjadinya pencoklatan pada buah maupun sayuran adalah enzim tirosinase . Untuk itu dirasa perlu untuk menilai aktiviias spesifik tirosinase darijamur merang agar dapat dipakat sebagai dasar untuk menenrukan cara-cara penundaan proses pencoklatan. Isolasi dilakukan dengan cara memblender 500 gjamur merang dengan penambahan aseton 300 ml sedikit demi sedikit sampai homogen kemudian disaring selanjutnya ditentukan aktivitas spes dengan menentukan unit aktivitas dan k.adar protein. Untuk uji aktivitas digunakan substrat L-tirosin sehingga menghasilkan dopakrom. Banyaknya dopakrom yang terbentuk ditentukan dengan spekirofotometer uv vis pada panjang gelombang 475 nm dan penentuan kadar protein dengan metode Lowry. Frakcinasi dengan amonium sulfat dibuat menjadi 4fraksi yaitu F1 (0-10%), P2 (10-20%), F3 (20-30%), dan P4 (30-60%). Hasil penelitian menunjukkan bahwa aktivitas spesifik tirosinase dan jamur merang untuk ekstra kasar 4,595 u/mg, F1 (0-10%) 5,841 u/mg, F2 (/0-20%) 6,020 u/mg; P3 (‘20- 30%) 4,034 u/mg dan P4 (30-60%) 5,435 u/mg. Aktifitas spesifik tirosinase jamur nierang ini masuk dalarn kategori tinggi dibandingkan dengan kentang.

Jamur merang (volvariella volvaceae), a certain mushroom species cultivated in the paady stems is a food commodity with a good nutritional value and has been cultivated in certain areas of Central Java. One of the obstacles found in this mushroom is the quich browning process that happens after being harvest. One of the causes of the browning process happening in many fruits and vegetables is the presence of tyrosinase enzyme. Thus, it is important to find the spec activity of the enzyme in the Jamur merang as a base data to find ways of postponing the browing process. Isolation of the enzyme was done by blending 500 gr of mushroom with 300 cc of aceton, added slowly and by little amount until a hemogenous mixture was achieved. The mixture was filtered and the specific activity was measured by determining the activity unit and its protein content. Substrate of L tyrosine was used for the activity test until dopacrome was produced. Dopacrome was determined using spectrophotometer with 475 nm wavelength. The protein cat content was determined using Lowry method. Four specimens were derived from fractination with ammonium sulphate, i.e: F1 (0-10%), F2 (1 0-20%), P3 (20-30%), F4 (30-60%). The result of the study revealed that the spec(uic activities of tyrosinase enzyme in the "Jamur merang" in rough extraction, F1, F2, F3 and P4 were 4,595 u/mg, 5,841 u/mg, 6,020 u/mg, 4,034 u/mg and 5,435 u/mg. The spec activity of the tvrosinase in this spesijlc mushroom can he catagorised as high compared to other food commodities such as potatoes.