Euphorbia Peroxidase Catalyzes Thiocyanate Oxidation in Two Different Ways, the Distal Calcium Ion Playing an Essential Role

Metal-free oxidative [2+2+1] heteroannulation of 1,7-enynes with thiocyanates toward thieno[3,4-c]quinolin-4(5H)-ones

A new metal-free oxidative [2+2+1] heteroannulation of 1,7-enynes with thiocyanates for producing thieno[3,4-c]quinolin-4(5H)-ones is presented. This reaction employs benzoylperoxide (BPO) as the oxidant and sodium thiocyanate as the sulfur source to enable the formation of three chemical bonds, two C-S bonds and one C-C bond, in a single reaction, and represents a new, practical access to S-heterocycles with the avoidance of the use of metal catalysts and excess bases.

Amine oxidase from Euphorbia characias: Kinetic and structural characterization

This minireview focuses on a plant copper/2,4,5-trihydroxyphenyl alanine quinone amine oxidase isolated from the latex of the shrub Euphorbia characias (ELAO). This enzyme has been investigated in terms of both molecular structure and kinetic mechanism. The characterization of this enzyme allowed us to identify specific amino acids and domains that play a key role in modulating substrate access into the active site not only for ELAO but also for other plant and mammalian amine oxidases. As mammalian amine oxidases are implicated in several physiological and pathological conditions, the deep structural characterization of their active site accession mechanisms could be the starting point for the development of enzyme modulators with high therapeutic potential. Thus, this paper gives structural/functional insights that open new perspectives in the research about the whole amine oxidase family.

The hypothiocyanite radical OSCN and its isomers

An elusive biologically relevant hypothiocyanite radical (OSCN) has been generated in the gas phase, and its reversible photoisomerization with two novel isomers OSNC and SOCN has been observed in cryogenic Ar and N₂ matrices at 2.8 K.

Biological Activities of Aerial Parts Extracts of Euphorbia characias

The aim of the present study was to evaluate antioxidant, antimicrobial, anti-HIV, and cholinesterase inhibitory activities of aqueous and alcoholic extracts from leaves, stems, and flowers of Euphorbia characias. The extracts showed a high antioxidant activity and were a good source of total polyphenols and flavonoids. Ethanolic extracts from leaves and flowers displayed the highest inhibitory activity against acetylcholinesterase and butyrylcholinesterase, showing potential properties against Alzheimer's disease. Antimicrobial assay showed that leaves and flowers extracts were active against all Gram-positive bacteria tested. The ethanolic leaves extract appeared to have the strongest antibacterial activity against Bacillus cereus with MIC value of 312.5 μg/mL followed by Listeria monocytogenes and Staphylococcus aureus that also exhibited good sensitivity with MIC values of 1250 μg/mL. Moreover, all the extracts possessed anti-HIV activity. The ethanolic flower extract was the most potent inhibitor of HIV-1 RT DNA polymerase RNA-dependent and Ribonuclease H with IC50 values of 0.26 and 0.33 μg/mL, respectively. The LC-DAD metabolic profile showed that ethanolic leaves extract contains high levels of quercetin derivatives. This study suggests that Euphorbia characias extracts represent a good source of natural bioactive compounds which could be useful for pharmaceutical application as well as in food system for the prevention of the growth of food-borne bacteria and to extend the shelf-life of processed foods.

Chitinase III in Euphorbia characias latex: Purification and characterization

This paper deals with the purification of a class III endochitinase from Euphorbia characias latex. Described purification method includes an effective novel separation step using magnetic chitin particles. Application of magnetic affinity adsorbent noticeably simplifies and shortens the purification procedure. This step and the subsequently DEAE-cellulose chromatography enable to obtain the chitinase in homogeneous form. One protein band is present on PAGE in non-denaturing conditions and SDS-PAGE profile reveals a unique protein band of 36.5 ± 2 kDa. The optimal chitinase activity is observed at 50 °C, pH 5.0. E. characias latex chitinase is able to hydrolyze colloidal chitin giving, as reaction products, N-acetyl-D-glucosamine, chitobiose and chitotriose. Moreover, we observed that calcium and magnesium ions enhance chitinase activity. Finally, we cloned the cDNA encoding the E. characias latex chitinase. The partial cDNA nucleotide sequence contains 762 bp, and the deduced amino acid sequence (254 amino acids) is homologous to the sequence of several plant class III endochitinases.

Euphorbia characias latex amine oxidase and peroxidase: interacting enzymes?

This minireview deals the enzymatic transformation of some amino acids as arginine and ornithine, amines as tyramine, putrescine, spermine and spermidine, and other substances as nitric oxide and thiocyanate. These reactions, catalyzed by two proteins purified from the latex of Euphorbia characias, a copper/quinone containing amine oxidase and a cationic peroxidase, show enzymatic activity interactions probably occurring between these proteins in Euphorbia latex.

Nitric oxide, substrate of Euphorbia characias peroxidase, switches off the CN(-) inhibitory effect

The oxidation of nitric oxide (NO) by Euphorbia characias latex peroxidase (ELP-Fe^III), in the presence or in the absence of added calcium, has been investigated. The addition of hydrogen peroxide to the native enzyme leads to the formation of Compound I and serves to catalyse the NO oxidation. The addition of NO to Compound I leads to the formation of Compound II and, afterwards, to the native enzyme spectrum. Under anaerobic conditions, the incubation of the native enzyme (ELP-Fe^III)with NO leads to the formation of the stable complex, showing a characteristic absorption spectrum (ELP-Fe^II–NO⁺). The rate of the formation of this complex is slower in the presence of calcium than in its absence, and the same applies to the rate of the formation of Compound II from Compound I, using NO as substrate. Finally, we demonstrate that NO protects ELP from the inactivation caused by CN⁻via a mechanism presumably requiring the formation of an enzyme-nitrosyl cyanide complex.

Calcium ions and a secreted peroxidase in Euphorbia characias latex are made for each other

This minireview deals of a protein, a class III secreted peroxidase, present as unique isoform in the latex of the perennial Mediterranean shrub Euphorbia characias. The paper reports on the molecular properties, on the structures (primary, secondary and tertiary), and on the catalytic mechanism of this enzyme. Here is also reported the extraordinary effect of calcium ions on the structure and on the enzyme activity of Euphorbia peroxidase. These ions can either enhance the catalytic efficiency of the enzyme toward some substrates or can regulate the ability of the enzyme to execute different metabolic pathways toward the same substrate. This review will give a valuable reference to the peroxidase fans and the general readers will find many thorough suggestions for future researches giving birth to new studies and important discoveries.