| Browning is one of the key factors that influence the shelf-life and product quality of the cultivated mushrooms. Tyrosinase (TYE) is generally recognized as the major enzyme responsible for the browning. However, systematic research in this field is still needed to pin point the specific roles of the enzyme plays. This study aimed at scrutiny into the relation between activity of TYE and browning of mushroom, and cloning of partial sequence of TYE cDNA for further genetic manipulation.Muskroom(Agricus bisporus Var.2796) slices were treated with p-hydroxybenzoic acid as inhibitor and peach kernel extracts as activator. Their browning progress was monitored using color-diffe -rence meter, and TYE activity as well as Laccase activity determined. The results revealed that:(1) Treating with inhibitor (p-hydroxybenzoic acid solution) reduced activity of TYE significantly during the storage. The average activity of TYE was reduced by 33.5 % in 4 days of ambient storage.(2) Consequently, inhibitor treatment reduced mushroom browning significantly. The L value of inhibitor treated samples was 26.2% higher than control after 4 days of ambient storage.(3) Peach kernel extracts did not significantly affect TYE activity .(4)The low activity and mild fluctuation of Laccase in mushroom suggested that laccase would not be the key enzyme resulting in browning of mushroom.(5) The strong correlation between accumulations of TYE activity and browning of mushroom, and the fact that the inhibition of TYEactivity resulted in the alleviation of browning, strongly suggested that TYE is the major enzyme responsible for browning in mushroom.(6)A fragment of TYE cDNA in mushroom was cloned, and its cloning plasmid pUC-TYE was constructed. Sequence analysis revealed two additional fragments of 62bp and 95bp at the 273bp and 461bp sites of the published sequence. The differences were probably due to alternative splicing of the mushroom TYE pre-mRNA.
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