Search results for "Nitrogen"

Nitrogen efficiency in wheat as affected by crop rotation, tillage and N fertilization.

2009

Structure-based engineering of strictosidine synthase: auxiliary for alkaloid libraries.

2007

SummaryThe highly substrate-specific strictosidine synthase (EC 4.3.3.2) catalyzes the biological Pictet-Spengler condensation between tryptamine and secologanin, leading to the synthesis of about 2000 monoterpenoid indole alkaloids in higher plants. The crystal structure of Rauvolfia serpentina strictosidine synthase (STR1) in complex with strictosidine has been elucidated here, allowing the rational site-directed mutation of the active center of STR1 and resulting in modulation of its substrate acceptance. Here, we report on the rational redesign of STR1 by generation of a Val208Ala mutant, further describing the influence on substrate acceptance and the enzyme-catalyzed synthesis of 10-m…

Construction and expression of a dual vector for chemo-enzymatic synthesis of plant indole alkaloids inEscherichia coli

2010

A dual vector (pQE-70-STR1-SG) containing coding regions of strictosidine synthase (STR1, EC 4.3.3.2) and strictosidine glucosidase (SG, EC 3.2.1.105) from the Indian medicinal plant Rauvolfia serpentina was constructed. Functional expression of the vector in Escherichia coli cells (M15 strain) was proven by isolation of prepurified enzyme extracts, which show both STR1 and SG activities. Incubation of the enzyme in the presence of tryptamine and secologanin delivered the indole alkaloid cathenamine, demonstrating functional co-expression of both STR1- and SG-cDNAs. Cathenamine reduction by sodium borohydride leading to tetrahydroalstonine revealed the chemo-enzymatic indole alkaloid synthe…

A facile chemoenzymatic approach: one-step syntheses of monoterpenoid indole alkaloids.

2010

Facile chemoenzymatic syntheses of cytotoxic monoterpenoid indole alkaloids with novel skeletons and multiple chiral centers are described. Synthesis of these alkaloids was achieved by a simple one-step reaction using strictosidine and 12-aza-strictosidine as the key intermediates. Strictosidines were prepared by coupling of secologanin with tryptamine and 7-aza-tryptamine, respectively, using the immobilized recombinant Rauvolfia strictosidine synthase. A detailed stereochemical analysis is presented herein. The results provide an opportunity for a chemoenzymatic approach that leads to an increased diversification of complex alkaloids with improved structures and activities.

3D-Structure and function of strictosidine synthase--the key enzyme of monoterpenoid indole alkaloid biosynthesis.

2008

Strictosidine synthase (STR; EC 4.3.3.2) plays a key role in the biosynthesis of monoterpenoid indole alkaloids by catalyzing the Pictet-Spengler reaction between tryptamine and secologanin, leading exclusively to 3alpha-(S)-strictosidine. The structure of the native enzyme from the Indian medicinal plant Rauvolfia serpentina represents the first example of a six-bladed four-stranded beta-propeller fold from the plant kingdom. Moreover, the architecture of the enzyme-substrate and enzyme-product complexes reveals deep insight into the active centre and mechanism of the synthase highlighting the importance of Glu309 as the catalytic residue. The present review describes the 3D-structure and …

Improved Expression of His6-Tagged Strictosidine Synthase cDNA for Chemo-Enzymatic Alkaloid Diversification

2010

Strictosidine synthase (STR1) catalyzes the stereoselective formation of 3alpha(S)-strictosidine from tryptamine and secologanin. Strictosidine is the key intermediate in the biosynthesis of 2,000 plant monoterpenoid indole alkaloids, and it is a key precursor of enzyme-mediated synthesis of alkaloids. An improved expression system is described which leads to optimized His(6)-STR1 synthesis in Escherichia coli. Optimal production of STR1 was achieved by determining the impact of co-expression of chaperones pG-Tf2 and pG-LJE8. The amount and activity of STR1 was doubled in the presence of chaperone pG-Tf2 alone. His(6)-STR1 immobilized on Ni-NTA can be used for enzymatic synthesis of stricto…

Crystallization and preliminary X-ray analysis of strictosidine synthase and its complex with the substrate tryptamine

2005

Strictosidine synthase (STR1) is a central enzyme that participates in the biosynthesis of almost all plant monoterpenoid indole alkaloids. After heterologous expression in Escherichia coli, crystals of STR1 and its substrate complex with tryptamine were obtained by the hanging-drop technique at 302–304 K with potassium sodium tartrate tetrahydrate as precipitant. All crystals belong to space group R3. The native STR1 crystals diffract to 2.95 Å and have unit-cell parameters a = b = 150.3, c = 122.4 Å. The tryptamine complex crystals diffract to 2.38 Å, with unit-cell parameters a = b = 147.3, c = 122.3 Å.

Effects of plant species in a horizontal subsurface flow constructedwetland – phytoremediation of treated urban wastewater withCyperus alternifolius …

2013

Abstract Plant species carry out a series of important biological, chemical and physical processes within a constructed wetland wastewater treatment system and make a significant contribution to wastewater purification. This paper compares two emergent macrophytes – Cyperus alternifolius L. and Typha latifolia L. – planted separately in a pilot horizontal subsurface flow system for the phytoremediation of treated urban wastewater in the West of Sicily (Italy). The total surface area of the three units within the pilot system was 99 m 2 . Six subunits were planted with two species and three subunits were left unplanted as the control. The main aim of the study was to demonstrate that, under …

The cockroach Blattella germanica obtains nitrogen from uric acid through a metabolic pathway shared with its bacterial endosymbiont.

2014

Uric acid storedin the fat bodyof cockroaches is a nitrogen reservoirmobilized in times of scarcity. The discovery of urease in Blattabacterium cuenoti, the primary endosymbiont of cockroaches, suggests that the endosymbiont may participate in cockroach nitrogen economy. However, bacterial urease may only be one piece in the entire nitrogen recycling process from insect uric acid. Thus, in addition to the uricolytic pathway to urea, there must be glutamine synthetase assimilating the released ammonia by the urease reaction to enable the stored nitrogen to be metabolically usable. None of the Blattabacterium genomes sequenced to date possess genes encoding for those enzymes. To test the host…

Infrequent promoter methylation of the MGMT gene in liver metastases from uveal melanoma.

2008

Uveal melanoma is associated with a high mortality rate once metastases occur, with over >90% of metastatic patients dying within less than 1 year from metastases to the liver. The intraarterial hepatic (iah) administration of the alkylating agent fotemustine holds some promise with response rates of 36% and median survival of 15 months. Here, we investigated whether the DNA-repair-protein MGMT may be involved in the variability of response to fotemustine and temozolomide in uveal melanoma. Epigenetic inactivation of MGMT has been demonstrated to be a predictive marker for benefit from alkylating agent therapy in glioblastoma. We found a methylated MGMT promoter in 6% of liver metastases fr…