Purification and characterization of proteases from the polychaete annelid Sabellaria alveolata (L.)

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Abstract
Eleven proteases have been purified to electrophoretic homogeneity from crude digestive fluid of polychaete annelids, Sabellaria alveolata. Purification steps were Sephadex G‐100 gel filtration, benzamidine‐cellulose and SBTI‐Sepharose (SBTI = soybean trypsin inhibitor) affinity chromatography, CM‐Sepharose and DEAE‐Sepharose ion‐exchange chromatography.Nine proteases have been purified in sufficient quantities for characterization. All are active at basic pH and are probably serine proteases, since they are inhibited by phenylmethylsulfonyl fluoride, specific chloromethyl ketone amino acids derivatives, but not by EDTA and p‐chloromercuribenzoate. They do not hydrolyse exopeptidase substrates.From their properties, they can be divided into five classes. A trypsin‐like protease, which hydrolyses only trypsin substrates and is inhibited by N‐tosyl‐l‐lysine chloromethyl ketone (TosLysCH2Cl), leupeptin and antipain. It differs from bovine trypsin by its very acidic isoelectric point (below 3.3) and its higher Mr (35000). A chymotrypsin‐like protease which hydrolyses only chymotrypsin substrates and is inhibited by TosPheCH2Cl, Z‐PheCH2Cl, chymostatin but only slightly by leupeptin and antipain. Its isoelectric point is below 3.3 and its Mr 31000. Two minor chymotrypsin‐like proteases with slightly broader specificity, since they hydrolyse trypsin substrates significantly and are much more inhibited by leupeptin. They have acidic isoelectric points (3.3 and 3.5) and slightly lower Mr (27000). Four proteases hydrolyse trypsin and chymotrypsin substrates equally well. Their chymotryptic character is, however, predominant since they are inhibited by TosPheCH2Cl and Z‐PheCH2Cl but not TosLysCH2Cl. They have similar Mr (27000) but isoelectric points ranging from 4.0 to above 9.1. The last one is very similar but has lower esterolytic activities. These proteases of broad specificity do not resemble any known serine protease since they differ from subtilisins by their sensitivity to TosPheCH2Cl.