Proteases present in shrimp processing waste are factors in the technology of shrimp. The distribution of proteolytic activity in shrimp parts was determined using hemoglobin and casein as substrates. The effects of various parameters upon activity of proteases in the inedible portion were determined using muscle protein as a substrate. Low pH active proteases from the hepatopancreas were characterized using column chromatography and inhibitors. A crude homogenate of shrimp processing waste showed maximum proteolytic activity on casein at pH 6.25, although activity was relatively uniform between pH 5.75 and 7.5. Hemoglobin digestion was greatest between pH 3 and 3.65. Specific activity was greatest in the foregut followed by the hepatopancreas and remainder of the inedible portion. Shrimp which contained food in their foreguts had greatest total activity in the foregut followed by the hepatopancreas. The order was reversed for shrimp which had not been feeding. Total activity was lowest in the inedible portion with digestive organs removed. Only negligible activity was detected in the muscle. Autolytic changes in a model system were studied where shrimp processing waste was the major protease source and muscle protein served as the major substrate. Activity data showed a major maximum at pH 3 and a minor broad maximum between pH 7 and 9. Maximum autolytic activity occurred at 50°C for pH 3 and at 55°C for pH 7.4. Incubation of the inedible portion at 65°C for 30 min was sufficient to inactivate the proteases. Proteases were unstable at low pH and 10 min on ice at pH 1.8 were required for inactivation. Autolysis at pH 3 was completely prevented by 10% NaCl while the inhibitory effects were less at pH 7.4. Protein solubility was decreased by NaCl at pH 3 and increased at pH 7.4. Heat-denatured muscle proteins were less susceptible to hydrolysis, possibly through a reduction in solubility. Changes occurred in the electrophoretic profile of soluble proteins (pH 7.4) from a muscle mixture which was incubated at 50°C. Changes also occurred when incubation mixtures contained inedible portion and these changes were more rapid than when inedible portion was absent. Low pH active proteases from the hepatopancreas were studied using hemoglobin as a substrate at pH 3.5. Gel filtration of a preparation from the hepatopancreas on Sephadex G-150 separated hemoglobin digesting activity in two distinct fractions. Chromatography on DEAE-cellulose also separated activity into two fractions and provided further evidence for the existence of at least two enzymes. Fractions from chromatography were unaffected by phenylmethyl sulphonylfluoride, unaffected or slightly activated by KCN, and greatly inactivated by p-chloromercuribenzoate. EDTA greatly activated all fractions. The result indicated that -SH groups are important for enzyme activity. A crude homogenate of the hepatopancreas and the major fraction from ion-exchange chromatography were most active on hemoglobin between pH 3 and 4. / Graduation date: 1975

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

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Typescript. / Thesis (Ph. D.)--University of Hawaii, 1965. / Bibliography: leaves 94-97. / [3], xi, 97 l mounted illus., tables

ix, 161 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1972

Thesis (Ph.D.) -- University of Adelaide, Dept. of Biochemistry, 1972.

Bibliography: pages 161-176. / Vibrio alginolyticus is a gram-negative aerobic bacterium that produces several extracellular serine proteases and a collagenase during the stationary growth phase. The aim of this study was to investigate alkaline serine protease production by this organism, and to attempt the cloning and expression of a V.alginolyticus protease gene in Escherichia coli.

A heat stable protease was identified as the cause of textural degradation in cooked arrowtooth flounder (Atheresthes stomias) muscle. Maximum proteolytic activity in the fish muscle was observed between 55°C and 60°C and myosin heavy chain appeared to be the primary substrate for the enzyme. Degradation of this myofibrillar protein at 55°C was extremely rapid and myosin heavy chain was completely hydrolyzed to peptide fragments smaller than actin, while actin itself was unaffected. A single strand 32kD proteolytic enzyme was extracted from the muscle and purified 125-fold. The enzyme was stable to freezing for up to 6 months. Activity of the semi-purified enzyme at 55°C was optimal against casein between pH 6.0 and 7.0. Sulfhydryl reagents p-chloromercuriphenylsulfonic acid, iodoacetate, iodoacetamide and cystatin were effective in inhibiting enzyme activity in casein assays. The serine protease inhibitors phenylmethylsulfonylfluoride and trypsin-chymotrypsin inhibitor appeared to activate enzyme activity against casein. Adenosine triphosphate was also an activator. Arrowtooth flounder was then considered as a raw material for surimi, since the surimi process provides for repeated washing of the minced muscle and a final mixing step during which inhibitory substances can be conveniently added. Arrowtooth muscle was monitored at all stages of surimi production. There was no evidence of myosin degradation on sodium dodecyl sulphate polyacrylamide electrophoretic gels at any time during surimi production or during the preparation of samples for testing. However, when the washed mince was incubated at 55°C, 12% residual proteolytic activity was observed. This level was sufficient to degrade the myosin component of surimi gels prepared from the control surimi to which no inhibitors had been added. The food grade substances tested for proteolytic inhibition were bovine blood plasma powder, egg white powder, whey protein concentrate, carrageenan and crude α₂-macroglobulin. Addition of plasma and/or egg white powders to control surimi resulted in a product that was comparable to pollock in functional properties as measured by gel strength, expressible moisture and fold tests. Electrophoretic comparison of surimi made with 1.0% or 2.0% plasma powder or egg white with surimi produced with 0.1% or 0.2% α₂-macroglobulin suggested that the plasma and egg white contributed gel enhancing effects in addition to protease inhibition. Carrageenan was not effective as either a protease inhibitor or gel enhancer. / Graduation date: 1992