Purification and characterization of phenoloxidase from brown shrimp (Penaeus aztecus)
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| Format: | Thesis Book |
| Language: | English |
| Published: |
1982.
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| Online Access: | Link to ProQuest Copy Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | Phenoloxidase is an enzyme which apparently contributes to the formation of melanin or "black spot" in shrimp held on ice. This enzyme was extracted from brown shrimp (Penaeus aztecus) heads, and purified by acetone precipitation, molecular sieving and ion-exchange chromatography. A five-fold purification was obtained, wth a 44% activity yield. The enzyme was found to have an optimum pH of 6.2, and to be stable at temperatures below 35(DEGREES)C. Below freezing, however, the enzyme was damaged irreversibly. The molecular weight of the enzyme, estimated by molecular sieving, was 213,000 dalton. Several chemicals were tested as potential inhibitors of the reaction. Among those found to be effective were phenylthiourea, sodium bisulfite, ascorbic acid, cysteine and methyl mercury. Other compounds tested which showed no inhibitory activity were sodium acid pyrophosphate (SAPP), sodium hexametaphosphate (SHP), sodium tripolyphosphate (STP) and tryptophan. Of special interest was the inability of N-ethyl-maleimide and Ellman's reagent, both of which bind strongly to sulfhydryl groups, to inhibit the reaction.To determine the naturally-ocurring phenols which may act as substrates for the reaction, extractions were made of shrimp heads. Only three different phenols could be demonstrated, one of which was identified as DOPA. None of the remaining two compounds appeared to be tyrosine. |
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| Item Description: | "Major subject: Food Science and Technology." Typescript (photocopy). Vita. |
| Physical Description: | x, 73 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 66-72). |