High and low molecular weight proteolytic activities in prawn (Metapenaeusbreviconis) muscle

Muscle extract of prawn (Metapenaeus brevicornis) expressed high azocoll ly tic activity compared to extracts of many other prawn varieties; the activi ty was also inhibited to a small extent by dithiothreitol. Ammonium sulphat e precipitation, subsequent extraction at pH 5.6 and chromatography reveale d the occurrence of two types of azocoll lytic activities: one, high molecu lar weight (630 kDa) and the other low molecular weight (<30 kDa) enzyme. T he former was stimulated by dithiothreitol whereas the latter was inhibited . SDS PAGE of high molecular weight preparation did not show homogeneity bu t the profile was similar to that of the low molecular weight fraction. Gel filtration of high molecular weight enzyme following incubation at high pH revealed the formation of low molecular weight fractions having activity t owards azocoll. Chymotrypsin-like activity associated with high molecular w eight enzyme was also susceptible to dissociation by high pH. Azocoll lytic activity of both enzymes was strongly inhibited by 1,10-phenanthroline.