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In crystallo activity tests with latent apple tyrosinase and two mutants reveal the importance of the mutated sites for polyphenol oxidase activity.

ABSTRACT: Tyrosinases are type 3 copper enzymes that belong to the polyphenol oxidase (PPO) family and are able to catalyze both the ortho-hydroxylation of monophenols and their subsequent oxidation to o-quinones, which are precursors for the biosynthesis of colouring substances such as melanin. The first plant pro-tyrosinase from Malus domestica (MdPPO1) was recombinantly expressed in its latent form (56.4?kDa) and mutated at four positions around the catalytic pocket which are believed to influence the activity of the enzyme. Mutating the amino acids, which are known as activity controllers, yielded the mutants MdPPO1-Ala239Thr and MdPPO1-Leu243Arg, whereas mutation of the so-called water-keeper and gatekeeper residues resulted in the mutants MdPPO1-Glu234Ala and MdPPO1-Phe259Ala, respectively. The wild-type enzyme and two of the mutants, MdPPO1-Ala239Thr and MdPPO1-Phe259Ala, were successfully crystallized, leading to single crystals that diffracted to 1.35, 1.55 and 1.70?Å resolution, respectively. All crystals belonged to space group P212121, exhibiting similar unit-cell parameters: a = 50.70, b = 80.15, c = 115.96?Å for the wild type, a = 50.58, b = 79.90, c = 115.76?Å for MdPPO1-Ala239Thr and a = 50.53, b = 79.76, c = 116.07?Å for MdPPO1-Phe259Ala. In crystallo activity tests with the crystals of the wild type and the two mutants were performed by adding the monophenolic substrate tyramine and the diphenolic substrate dopamine to crystal-containing drops. The effects of the mutation on the activity of the enzyme were observed by colour changes of the crystals owing to the conversion of the substrates to dark chromophore products.

SUBMITTER: Kampatsikas I

PROVIDER: S-EPMC5544008 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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In crystallo activity tests with latent apple tyrosinase and two mutants reveal the importance of the mutated sites for polyphenol oxidase activity.

Kampatsikas Ioannis I Bijelic Aleksandar A Pretzler Matthias M Rompel Annette A

Acta crystallographica. Section F, Structural biology communications 20170728 Pt 8

Tyrosinases are type 3 copper enzymes that belong to the polyphenol oxidase (PPO) family and are able to catalyze both the ortho-hydroxylation of monophenols and their subsequent oxidation to o-quinones, which are precursors for the biosynthesis of colouring substances such as melanin. The first plant pro-tyrosinase from Malus domestica (MdPPO1) was recombinantly expressed in its latent form (56.4 kDa) and mutated at four positions around the catalytic pocket which are believed to influence the ...[more]

PMID: 28777094

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Project description:γδ T cells are lymphocytes that function in both innate and adaptive immune responses, and our laboratory has previously reported that both bovine and human γδ T cells are primed for secondary responses by tannin components of the unripe apple peel (APP). In this report we began to investigate the mechanism by which priming occurs. We performed a microarray analysis on sorted bovine γδ T cells treated with APP and observed significant increases in transcripts encoding select inflammatory cytokines, such as GM-CSF, IL-8, and IL-17, but not markers of TCR stimulation such as IFNγ. When injected into the gut of mice, APP induced a robust influx of neutrophils into both the blood and peritoneum as measured by FACS. Importantly, both GM-CSF and IL-8 proteins were detected in these animals. Further studies were performed using the human γδ T cell-line MOLT-14, as large numbers of cells were required for subsequent experiments. Using these cells we found that both the GM-CSF and IL-8 mRNAs were significantly upregulated and stabilized in cells treated with APP. Finally, we show that the ERK1/2 MAPK pathway was activated in APP-treated MOLT-14 cells, and that this pathway plays a role in the mRNA stabilization we observed. Together, our data describe a unique inflammatory response in bovine, murine, and human γδ T cells in response to APP, and suggest that mRNA stability mechanisms could account for the priming phenotype we previously observed.APP has a distinctive gamma delta T cells specific priming activity. Keywords: comparison of 2 treatment types, tannin, gamma delta T cells To begin to understand the effects of APP in innate immunity, we investigated the global gene expression profiles of stimulated bovine gamma delta T cells. Peripheral blood from 2 neonatal bovine calves was collected. gamma delta T cells were sorted to >97% purity using a FACS Vantage. Cells were placed in culture and stimulated with either an aqueous extract of APP (42.2ug/ml) or PBS for 4 hours after which RNA was extracted and processed for microarray analysis following standard protocols from Affymetrix.

Dataset Information

In crystallo activity tests with latent apple tyrosinase and two mutants reveal the importance of the mutated sites for polyphenol oxidase activity.

Publications

In crystallo activity tests with latent apple tyrosinase and two mutants reveal the importance of the mutated sites for polyphenol oxidase activity.

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