Purification and properties of three proteases from the larvae of the brine shrimp Artemia salina.

Three proteases, termed A, B and C, have been characterized and partially purified from Artemia salina larvae. Enzyme A is active on benzyloxycarbonyl L-leucin p-nitrophenyl ester (Km = 53 micron, determined at pH 8 and 37 degrees C) but not on alpha-N-benzoyl-DL-arginine p-nitroanilide and is strongly inhibited by micron concentrations of phenylmethylsulfonylfluoride. Enzymes B and C are active on alpha-N-benzoyl-L-arginine p-nitroanilide (Km = 20 and 11 micron, respectively) but not on benzyloxycarbonyl-L-leucine p-nitrophenyl ester and B, but not C, is inhibited by mM concentrations of phenylmethylsulfonyfluoride. Enzymes A, B and C are optimally active at alkaline pH values, do not require either metal ions or -SH groups for their catalytic activity and have molecular weights of 38 000, 33 000 and 34 000, respectively. After heating for 5 min at pH 7.5 and in the presence of 0.7 M KCl half inactivation of proteases A, B and C was attained at 60, 52 and 45 degrees C, respectively.