High-molecular-weight serine proteinase from lobster muscle that degrades myofibrillar proteins
✍ Scribed by Mykles, Donald L.
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 829 KB
- Volume
- 250
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
A latent alkaline serine proteinase (ASP) has been extracted from the soluble fraction of lobster claw and abdominal muscles. The enzyme, which was irreversibly activated 30to 40-fold by brief (2-3 min) heating at 60"C, had an optimal caseinolytic activity at pH 7.75. Its molecular weight was estimated to be 740,000 by gel filtration chromatography. Serine protease inhibitors (diisopropylfluorophosphate, phenylmethanesulfonyl fluoride, soybean trypsin inhibitor, aprotinin, benzamidine, and chloromethyl ketones) suppressed ASP activity 22 to 70%. In addition, sulfhydryl-blocking reagents and hemin inhibited activity 69 to 100%; leupeptin and E-64, however, did not. Pepstatin A, ethylenediaminetetraacetate, and adenosine triphosphate were without effect. These results suggest that the lobster ASP is a serine proteinase that contains one or more sulfhy-dry1 groups essential for catalysis. ASP was stimulated by dithiothreitol and inhibited by CaC1, and oleic and linoleic acids. The enzyme was partially activated by low concentrations of sodium dodecyl sulfate; 0.05% produced activities 13% of that of preparations heated at 60°C. Neither poly-L-lysine, urea, dimethylsulfoxide, oleic acid, linoleic acid, nor N-ethylmaleimide activated the enzyme. The ASP degraded most myofibrillar proteins, but showed a preferential hydrolysis of paramyosin, troponin-I and -C, and myosin a light chain.