Copper metallothionein (Cu-MT) was extracted from the induced biomass of Aspergillus niger. The crude extract (FI), obtained by cell homogenization, was partially purified by heat treatment (FII) and ultrafiltration (FIII). Further purification of the Cu-MT extract by affinity chromatography resulted in three major fractions, FIVa, FIVb and FIVc, of which fraction FIVc was considered to be the Cu-MT extract fraction. Fraction FIVc was re-chromatography on affinity chromatography and the eluted fraction showed a single peak (FIVc'). Spectrophotometric analysis of fraction FIVc' demonstrated a maximum absorption peak at 268 nm. Native and denatured electrophoretic analysis of fraction FIVc ' showed the presence of a single band with an estimated molecular weight of 9.5 and 10.0 kDa, respectively. Inhibition of mushroom tyrosinase (PPO) by the Cu-MT extracts was investigated, using selected phenolic substrates, including catechin, chlorogenic acid, catechol, 4-methylcatechol, caffeic acid, L-3,4-dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, 3-( p-hydroxyphenyl) propionic acid, p-hydroxyphenylpyruvic acid, p- and m-cresol. The results showed that the inhibitory effect of the Cu-MT extract increased with the degree of purification. The results revealed that the Cu-MT extracts were effective inhibitors of PPO activity and the best inhibitory effect was demonstrated with catechin as substrate; however, PPO activity was not inhibited by the Cu-MT extract when p-hydroxyphenylpyruvic acid and p- and m-cresol were used as substrates. The results also showed that the Cu-MT extracts exhibited different types of inhibition, including mixed, competitive and uncompetitive on PPO activity. In addition, the experimental findings indicated that the nature and degree of enzymatic inhibitions by the Cu-MT extracts were dependent upon the structural nature of the substrates as well as the methods including, spectrophotometer and polarograph, used for the detection of enzyme
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.29900 |
| Date | January 1999 |
| Creators | Hossain, Abzal. |
| Contributors | Kermasha, Selim (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Food Science and Agricultural Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001686942, proquestno: MQ55068, Theses scanned by UMI/ProQuest. |
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