RESULTS:
1 - 6 of 6 for ""DOPA""
Sucrose Isomerase and Its Mutants from Erwinia rhapontici Can Synthesise α-Arbutin
Sucrose isomerase (SI) from Erwinia rhapontici is an intramolecular isomerase that is normally used to synthesise isomaltulose from sucrose by a mechanism of intramolecular transglycosylation. In this study it was found that SI could synthesise α-arbutin using hydroquinone and sucrose as substrates via an intermolecular transglycosylation reaction. Five phenylalanine residues (F185 F186 F205 F297 and F321) in the catalytic pocket of SI were chosen for sitedirected mutagenesis. Mutants F185I F321I and F321W whose hydrolytic activities were enhanced after the mutation could synthesise α-arbutin through intermolecular transglycosylation with a more than two-fold increase in the molar transfer ratio compared with wild type SI. The F297A mutant showed a strong ability to synthesise a novel α-arbutin derivative and a four-fold increase in its specific activity for intermolecular transglycosylation over the wild type. Our findings may lead to a new way to synthesise novel glucoside products such as α-arbutin derivatives by simply manipulating the Phe residues in the catalytic pocket. From the structure superposition our strategy of manipulating these Phe residues may be applicable to other similar transglycosylating enzymes.
Purification, cDNA Clone and Recombinant Expression of Foot Protein-3 from Mytilus coruscus
Mussels Mytilus coruscus can adhere to various solid surface in the presence of moisture. Mussel foot protein-3 (mfp-3) has been suggested as the main adhesive protein in the plaques closest to the adhesion interface and been the focus of substantial biomaterials development research within the last decade. The byssal plaques of M. coruscus were accumulated and variants of a family known as mcofp3 (Mytilus coruscus foot protein 3) were purified from acetic acid/urea extracts of plaques with their N-terminal sequences determined thereafter. The cDNA sequence coding for the mcofp3 precursor was obtained from M. coruscus foot cDNA library. These precursors contain a putative signal peptide of 24 residues a mature peptide sequence of 41-56 amino acids rich in Tyr Gly Pro and Asn. The recombinant mcofp3 fused with a hexa-histidine affinity ligand was successfully expressed through an Escherichia coli expression system and the recombinant mcofp3 was purified using affinity chromatography followed by reverse phase high performance liquid chromatography (HPLC). The DOPA content and adhesive properties of purified recombinant mcofp3 with or without tyrosinase modification were compared with the native mcofp3. These assays showed that recombinant mcofp3 has significant adhesive ability and may be useful as a bioadhesive in medical or underwater environments.
Targeting Parkinson's - Tyrosine Hydroxylase and Oxidative Stress as Points of Interventions
Parkinson's disease (PD) is characterized by the progressive loss of the dopaminergic neurons leading to decrease in striatal dopamine (DA) levels. In the present review our focus was on recent advances in the treatment procedures of PD to achieve an increase in deficient tyrosine hydroxylase (TH) activity and/or expression. Stimulation of residual TH activity by the cofactors 6R-L-erythro-tetrahydrobiopterin (BPH4) or NADH or by brain transplant of natural TH-containing cells (fetal substantia nigra) or genetically engineered TH-containing cells has been tried experimentally and clinically lately. As a promising approach to the gene therapy intrastriatal expression of DAsynthesizing enzymes through transduction with separate adeno-associated virus (AAV) vectors/ marrow stromal cells (MSCs) or nonviral intravenous administration of rat transferrin receptor monoclonal antibody (TfRmAb)-targeted PEGylated immunoliposomes (PILs) has been found to be effective in animal models. Oxidative stress has been identified as one of the intermediary risk factors that could initiate and/or promote degeneration of DA neurons. TH itself is a prime target of oxidative/nitrosative injury. Certain superoxide dismutase and catalase mimetic prevented nitration of TH in cultured dopaminergic neurons. Therefore development of therapeutic agents that can prevent formation of or specifically remove nitrating agents without interfering with normal neuronal function may protect protein from inactivation and provide means of limiting neuronal injury in PD. Non-pharmacological approaches such as diet therapy or use of active constituents of plants and phytomedicines have also emerged as a new - area of high interest. New treatment strategies for TH dysfunction rectification a provision for neuroprotection in PD seem to be on the horizon with many therapies under investigation.
Practical Synthesis of DOPA Derivative for Biosynthetic Production of Potent Antitumor Natural Products, Saframycins and Ecteinascidin 743
A practical synthetic route of DOPA derivative 2 which should be useful for direct biosynthetic production of potent antitumor natural products saframycins and ecteinascidin 743 was established. The developed strategy features i) easy-to-handle reactions without special care upon both dryness and inert atmopsphere and ii) the facile HPLC-free purification of 2 via recrystallization enabling scalable synthesis of 2.
A Case of Doxycycline-induced Melanin in the Gingiva Tissue: Case Report
Background: Gingival pigmentation is a discoloration of the gingiva due to a variety of lesions and conditions associated with several endogenous and exogenous etiologic features. Objective: The purpose of this study is to describe a report of gingival pigmentation in a patient who used doxycycline. Case Report: A 21-year-old Caucasian female was under dermatological treatment and antibiotic therapy with doxycycline 100 mg (one time a day) for 90 days. She presented brown pigmentation at the gingival margin on the facial surfaces of the upper and lower anterior incisors and premolars. The patient was evaluated by immunohistochemical (S-100 Melan-A and HMB-45) and histopathologic analyses and clinical history. Blood levels of malondialdehyde (MDA) glutathione (GSH) and superoxide dismutase (SOD) were analyzed by UV/Vis spectroscopy. The adrenaline noradrenaline and dopamine in blood were analyzed by high-performance liquid chromatography (HPLC); dehidroepiandrosterone (DHEA) in serum by radioimmunoassay; and luteinizing hormone (LH) and 25-Hydroxyvitamin D by chemiluminescence. Hematoxylin-eosin stained sections revealed keratinocytes with pigment compatible with melanin. The Fontana-Masson staining was positive in melanophages and in some basal keratinocytes. S-100 Melan A and HMB-45 were confirmed as positive markers of melanocytic differentiation in gingival tissue. We observed a significant increase in malondialdehyde (p#130;0.05) and a decrease in superoxide dismutase levels (p#130;0.05). The dopamine value was found to be 15 pg/ml (reference value ≤ 10 pg/ml). Conclusion: The use of doxycycline is associated with an increase in oxidative stress and of dopamine with melanin pigments in the gingival tissue. This case report showed a cause-effect relationship between exposure to doxycycline and pigmentation of the marginal gingiva.
Synthesis of Cross-linkable 2,5-Diketopiperazine Derivatives
Synthesis of cross-linkable diketopiperadine derivatives is described. Cross-linkable aamino acid methyl esters were subjected to peptide synthesis with Boc-protected glycine or L-tyrosine. No protection of cross-linkable functional groups (catechol and phenylazide) is necessary for the construction of diketopiperazine skeleton.