Studies on the influence of small molecule factor(s) on protease activities in Norway lobster (Nephrops norvegicus)

The interactions of small molecule(s) and proteases in the suggested multiple component process of phenolase activation in Norway lobster (Nephrops norvegicus) were studied. observed that protease I is mainly a visceral protease, whilst proteases II and III exist in approximately equal amounts in viscera and flesh, respectively. found that the small molecule factor(s) (molecular weight less than 10 000) inhibited proteases I, II and III at pH 6.7 and 8.2, except when it was freshly prepared and then it activated only protease III and only at pH 8.2. This indicates that the small molecule(s) may be modified on storage. found that the small molecule factor(s) is primarily water-soluble and heat-stable, with heating resulting in a similar change to storage in its effect on proteases. Treatment of the small molecule filtrate with a cation-exchanger also increased the inhibition effect on proteases. However, whilst treatment with an anion-exchanger at pH 8.2 reduced inhibition, treatment at pH 4.0 restored activation of protease III. These results also infer that the small molecule factor(s) is modified on storage or exists in two forms.