Purification and characterisation of phosphorylase from muscle of Tilapia (Tilapia mosambica)

Phosphorylase from muscle of tilapia (Tilapia mosambica) was extracted by water and purified by ammonium sulphate precipitation, centrifugation and repeated recrystallisation. Electro-phorogram of the enzyme preparation showed a single band near origin. The enzyme showed optimum pH and temperature at 6.1 and 37°C respectively. Glucose and glucose-6-phosphate were found to be competitive inhibitors of the enzyme. Maltose and starch acted as primers for the phosphorylase reaction like glycogen.

Distribution of phosphorylase in some fish and shell fish

Phosphorylase content in the muscle of some fish and shell fish were estimated. Jew fish (Johnius dussumeri) and 'sea naran'(Penaeus indicus) recorded the highest enzyme content among the fish and shell fish studied. As phosphorylase is the key enzyme in glycogenolysis, which is the energy source of fish for muscular activity, the possible role of phosphorylase content as an index of muscular capacity and post-mortem autolysis is discussed.

Chemical changes in skin mucin as an index of early stages of spoilage in fish

Results of a preliminary investigation on the overall chemical nature of fish skin mucin in lung fish, Clarias batrachus, with special reference to water soluble low molecular weight compounds, are presented. Changes observed during room temperature spoilage have been studied with a view to present a new approach towards the assessment of freshness in fish inspection. pH of the mucin was distinctly alkaline (8.2) and remained unchanged during spoilage. Much of the nitrogen was found to be present in the glycoprotein fraction. Free amino acids and purine bases were present in appreciable quantities in the aqueous extracts which registered a significant increase after 10 hrs. Post-mortem increase in total solids was accompanied by a slight rise in protein nitrogen which may indicate tissue breakdown. Increase in TVN was also observed to occur earlier in the outside mucin as compared to the inside muscle. Presence of free sugars or sialic acid could not be confirmed nor was there any indication of cholesterol and lipoid material as stated in earlier literature.