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PubMed1998

Identification of arg-30 as the essential residue for the enzymatic activity of Taiwan cobra phospholipase A2.

Taiwan cobra (Naja naja atra) phospholipase A2 (PLA2) was inactivated by arginine-specific reagents, phenylglyoxal and 1, 2-cyclohexanedione. Kinetic analyses of the modification reaction revealed that the inactivation of PLA2 followed pseudo-first-order kinetics and the loss of activity was correlated with the incorporation of one molecule of modification reagent per PLA2 molecule. This was confirmed by the results of amino acid composition determination, that showed that a marked decrease in enzymatic activity was associated with the modification of one arginine residue. Tryptic cleavage of the modified protein and microsequencing revealed that Arg-30 was the functionally essential residue. The incorporation of a modifier into the PLA2 did not significantly affect the secondary structure of the enzyme, as revealed by the CD spectrum, and Ca2+-binding of the modified PLA2 was unaffected. Nevertheless, the nonpolarity of the active site of PLA2 markedly decreased with the arginine modification, as evidenced by the decreases in the enhancement of Trp and 8-anilinonaphthalene sulfonate fluorescence. These results, together with those of X-ray crystallographic analysis of N. naja atra PLA2 [Scott et al. (1990) Science 250, 1541-1546], demonstrate that Arg-30 is one of the residues involved in the interfacial binding of a PLA2 molecule with its substrate.

Animals↗
PubMed1976

The reactive site of eggplant trypsin inhibitor.

The reactive site peptide bond of the eggplant inhibitor against trypsin [EC 3.4.21.4] was identified by chemical modifications with 1,2-cyclohexanedione, 2,4,6-trinitrobenzenesulfonic acid, acetic anhydride and glyoxal, and by sequential treatments with trypsin and carboxypeptidase B [EC 3.4.12.3]. The inhibitor was significantly inactivated by chemical modifications of arginine residues, but was not affected by lysine modifications. Free arginine was released from the trypsin-modified inhibitor by carboxypeptidase B digestion, accompanied by a marked loss of inhibitory activity. A serine residue was newly exposed at the N-terminal amino acid of the inhibitor after modification with trypsin. The reactive site of the inhibitor against trypsin was concluded to be an arginylseryl bond. The inhibitor was completely inactivated by full reduction of its disulfide bonds.

Anhydrides↗
PubMed1977

Essential arginyl residues in yeast phosphoglyceromutase.

Inactivation of yeast phosphoglyceromutase (tetramer) with 1,2-cyclohexanedione correlates with the modification of six arginyl residues per mole of the enzyme. Protection experiments using 3-phosphoglycerate suggest that four arginyl residues (one residue per subunit) are involved in the binding of the substrate to the enzyme. The modified enzyme reversibly regained its activity upon incubation with hydroxylamine. The reactivity of lysyl residues which have been shown to be involved in the active site is markedly reduced in the enzyme inactivated with 1,2-cyclohexanedione, indicating that the lysyl and arginyl residues are in close proximity in the active site.

Arginine↗
PubMed2002

Occurrence and localization of apocarotenoids in arbuscular mycorrhizal plant roots.

The core structure of the yellow pigment from arbuscular mycorrhizal (AM) maize roots contains the apocarotenoids mycorradicin (an acyclic C14 polyene) and blumenol C cellobioside (a C13 cyclohexenone diglucoside). The pigment seems to be a mixture of different esterification products of these apocarotenoids. It is insoluble in water and accumulates as hydrophobic droplets in the vacuoles of root cortical cells. Screening 58 species from 36 different plant families, we detected mycorradicin in mycorrhizal roots of all Liliopsida analyzed and of a considerable number of Rosopsida, but also species were found in which mycorradicin was undetectable in mycorrhizal roots. Kinetic experiments and microscopic analyses indicate that accumulation of the yellow pigment is correlated with the concomitant degradation of arbuscules and the extensive plastid network covering these haustorium-like fungal structures. The role of the apocarotenoids in mycorrhizal roots is still unknown. The potential C40 carotenoid precursors, however, are more likely to be of functional importance in the development and functioning of arbuscules.

Carbohydrate Sequence↗
PubMed1986

The ultrapurification of indium-111 for radiotracer studies.

We have developed a procedure for the ultrapurification of 111In. A dried sample of 111InCl3 is dissolved in 1 ml of a freshly prepared KI solution of 4% in 4 N H2SO4. After 3 ml of anhydrous diethylether has been mixed well with the aqueous and centrifuged for 5 minutes at 2000 X g, the iodide salt of 111In is recovered with the organic solvent layer at approximately 92% of the original radioactivity. The organic phase is evaporated under a gentle stream of inert gas. After the sublimation of iodine, 111In is dissolved in a solvent of choice. The extraction is highly selective for In and separates it from, at least, Fe, Al, and Zn, principle associated cationic contaminants.

Cyclohexanones↗
PubMed2002

Tyrosinemia I, a model for human diseases mediated by 2-oxoacid-utilizing dioxygenases: hepatotoxin suppression by NTBC does not normalize hepatic collagen metabolism.

OBJECTIVES: Medical treatment of tyrosinemia I relies on the herbicide NTBC [Orfadin 2-(2-nitro-4-trifluoromethylbenzoyl)-cyclohexane-1,3-dione], an inhibitor of plant and mammalian 2-oxoacid-utilizing dioxygenases with a collective catalytic cycle ('HAG' mechanism). We hypothesize that NTBC-treated tyrosinemia I is a human model for the pathogenic role of two major enzymes in this class, 4-hydroxyphenylpyruvate dioxygenase (4-HPPD; EC 1.13.11.27) and prolyl 4-hydroxylase (P4-H; E.C. 1.14.11.2), essential for tyrosine and collagen metabolism, respectively. METHODS: In a patient with established tyrosinemia I, we monitored the in vivo activities of 4-HPPD and P4-H via five biomarkers before and during NTBC medication. Hypothesis testing at the molecular level was performed by computational modeling of NTBC binding to the crystal structure-derived active site of 4-HPPD, and then relating these findings to our experimental results and to known P4-H data. RESULTS: NTBC rapidly normalized the biomarkers for 4-HPPD activity. However, those for P4-H activity remained uniformly elevated after one hundred days on NTBC, the PIIINP biomarker even increasing above its grossly abnormal, initial level. This selective enzyme inhibition despite a collective catalytic cycle is attributed to the conformation of NTBC, which only fits the active site of 4-HPPD, as confirmed by its crystal structure. CONCLUSIONS: Normalization of hepatic collagen formation, highly desirable in all fibrotic liver diseases, is not achieved by NTBC in tyrosinemia I. By establishing the molecular cause for this failure, our results also establish a rational approach to identify inhibitors that achieve that goal, either by joint 4-HPPD / P-4H inhibition, or by inhibition of only P-4H.

4-Hydroxyphenylpyruvate Dioxygenase↗
PubMed1997

Endogenous arachidonic acid release and pancreatic amylase secretion.

Recent studies have suggested the involvement of phospholipase A2 (PLA2) in pancreatic amylase secretion. The present study was designed to investigate the secretory role of arachidonic acid (AA) in carbachol (Cch)-stimulated rat pancreatic acini and its origin. From enzymatic assays, PLA2 and diacylglycerol (DAG) lipase were activated by Cch and respectively inhibited by the PLA2 inhibitors, mepacrine and aristolochic acid, and by the DAG lipase inhibitor, RHC 80267. Melittin-activated PLA2 activity was also inhibited by the PLA2 inhibitors. Cch-stimulated endogenous AA release from pancreatic acini was partially inhibited by 150 microM RHC 80267 and by 150 microM mepacrine or 200 microM aristolochic acid and totally inhibited by a combination of the two enzyme inhibitors. Exogenous AA caused amylase release in a concentration-dependent manner. Eicosatetraynoic acid (a cyclooxygenase and lipoxygenase inhibitor), significantly increased basal and Cch-induced AA release and amylase secretion. RHC 80267 and the PLA2 inhibitors separately and partially suppressed Cch-stimulated amylase secretion, with an additive effect observed when the DAG lipase and the PLA2 inhibitors were combined. A combination of RHC 80267, mepacrine, or aristolochic acid and the phospholipase C (PLC) inhibitor U73122 completely inhibited Cch-stimulated amylase secretion. Finally, the PLA2 activator melittin-stimulated amylase secretion was blocked by the two PLA2 inhibitors. We conclude that exogenous and endogenous AA can induce amylase secretion. Therefore, AA released from either PLC-DAG lipase or PLA2 pathways can be considered an additional and important intracellular mediator of amylase secretion.

Amylases↗
PubMed1995

Diagnosis and management of tyrosinemia type I.

Hereditary tyrosinemia type I (HTI) (MIM 276700) is an autosomal recessive disorder caused by deficiency of fumarylacetoacetase (EC 3.7.1.2), which is the last enzyme in the tyrosine degradation pathway. The enzyme block causes accumulation of toxic metabolites in the liver and kidneys, which are the organs where tyrosine is mainly degraded. The disorder is characterized by severe liver disease, which either causes liver failure in infancy or may take a more protracted course, with death often occurring during childhood or adolescence because of hepatoma development. Treatment with a diet restricted in phenylalanine nd tyrosine does not prevent progression of the liver disease and development of hepatocellular carcinoma. Liver transplantation was previously the only option for these patients. Important achievements from metabolic and molecular biology studies of the disease include a new treatment for patients with HTI using an enzyme inhibitor, detection of self-induced correction of the genetic defect in regenerative liver nodules in HTI patients, identification and development of useful animal models for HTI, and studies of the molecular genetics of HTI. These advances will have great implications for our understanding of pathogenetic mechanisms, which is the basis for improved diagnostic methods and improved treatment of patients with HTI.

4-Hydroxyphenylpyruvate Dioxygenase↗
PubMed2003

Novel nuclear factor kappa B activation inhibitor prevents inflammatory injury in unilateral ureteral obstruction.

PURPOSE: We determined whether the novel nuclear factor kappa B activation inhibitor dehydroxymethylepoxyquinomicin (DHMEQ), which is derived from epoxyquinomicin C, affects renal inflammatory responses in unilateral ureteral obstruction. MATERIALS AND METHODS: DHMEQ (8 mg./kg.) was administered to rats 1 day after unilateral ureteral obstruction and every day thereafter. Kidneys were harvested at day 7 after unilateral ureteral obstruction. Tissue nuclear factor kappa B activity and transforming growth factor-beta were determined by electrophoretic mobility shift assay and bioassay using mink lung epithelial cells, respectively. Renal tubular proliferation and apoptosis were detected by immunostaining proliferating cellular nuclear antigen and the TUNEL (Intergen, Purchase, New York) assay, respectively. Leukocyte infiltration was detected by immunostaining for CD45. Fibrosis was assessed by measuring tissue hydroxyproline content. RESULTS: Unilateral ureteral obstruction for 7 days significantly activated nuclear factor kappa B, induced tubular apoptosis, proliferation and interstitial fibrosis in the obstructed kidney of the control group compared with their unobstructed counterparts (30.3 +/- 4.5 nuclei per high power field versus 1.7 +/- 0.4, 25.7 +/- 3.3 nuclei per high power field versus 3.2 +/- 0.4 and 6.2 +/- 0.3 micromol. hydroxyproline per gm. tissue versus 3.4 +/- 0.1, respectively). Conversely daily administration of DHMEQ (8 mg./kg.) significantly inhibited nuclear factor kappa B activation and decreased mean tubular apoptosis (9.5 +/- 2.1 nuclei per high power field), proliferation (10.2 +/- 2.4 nuclei per high power field) and interstitial fibrosis (4.9 +/- 0.4 micromol. hydroxyproline per gm. tissue) in the obstructed kidney. CONCLUSIONS: Specific inhibition of nuclear factor kappa B can prevent inflammatory renal responses, suggesting that targeting nuclear factor kappa B activation may be feasible for preventing inflammatory kidney diseases.

Animals↗
PubMed2006

Image analysis as an adjunct to sodium rhodizonate test in the evaluation of gunshot residues: an experimental study.

It is important to investigate the clothing, as well as the body, to determine the range of fire of entry wounds in firearm injuries. Clothing can affect the amount of gunshot residues (GSR) reaching the body and their distribution. The amount and distribution of the GSR also vary according to the distance between the firearm and the target. Sodium rhodizonate test provides valuable data when clothing is available for examination. In the absence of clothing, light microscopic examinations may add additional information regarding the range of fire. In this study, a sodium rhodizonate test was done on 80 garment samples containing the bullet entrance. The 80 calfskin samples were processed histologically and were stained using Alizarin Red S. These were also evaluated with computer-assisted image analysis. Gross residues were seen on military camouflage clothing in samples from < or = 45-cm group. White flannel undershirts under the military camouflage contained rhodizonate-positive particles only around the contact wounds. With image analysis, however, the residues could be detected also in the skin samples of the 2.5-cm- and 5-cm-range groups. We suggest that the image analysis can be combined with other techniques and it can provide valuable data in the determination of entry wounds and also in the estimation of firing distance.

Clothing↗
PubMed2006

Control of allograft rejection by applying a novel nuclear factor-kappaB inhibitor, dehydroxymethylepoxyquinomicin.

BACKGROUND: Nuclear factor (NF)-kappaB plays a crucial role in lymphocyte activation, proliferation, and survival. We examined the immunosuppressive effect of a newly developed NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ) in allotransplantation. METHODS: Purified C57BL/6 (H-2b) T cells were used for in vitro studies examining activation, proliferation, cytokine production and nuclear NF-kappaB and nuclear factor of activated T cells (NFAT) protein levels. A fully major histocompatibility complex incompatible BALB/c (H-2d)-to-C57BL/6 mice cardiac transplantation model was utilized for in vivo studies. DHMEQ was given intraperitoneally to transplant recipients at a various dose starting from day 0. In some, DHMEQ was administered concomitantly with tacrolimus. RESULTS: DHMEQ significantly suppressed alphaCD3 + alphaCD28 monoclonal antibody-triggered T-cell proliferation, CD25/CD69 expressions, and both interleukin-2 and interferon (IFN)-gamma production in a dose-dependent fashion. DHMEQ blocked nuclear translocation of NF-kappaB but not NFAT in activated T cells. Combined treatment with DHMEQ and tacrolimus significantly suppressed T cell activation as compared to that of mono-therapy with either agent alone. Single DHMEQ treatment moderately prolonged cardiac allograft survival. Further, combination of DHMEQ plus tacrolimus markedly prolonged graft mean survival time (MST) to 59.5 days when compared to either DHMEQ (MST: 10 days) or tacrolimus (MST: 13 days) treatment alone. Such effect was associated with inhibition of mixed lymphocyte reaction against donor antigen, IFN-gamma producing splenocytes and graft cellular infiltration as examined at 5 and 12 days posttransplantation. CONCLUSION: DHMEQ inhibits nuclear translocation of NF-kappaB but not NFAT in activated T cells, and prolongs allograft survival. Blocking both NF-kappaB and NFAT by DHMEQ and tacrolimus induces potent immunosuppression, which may become a new modality in controlling allograft rejection.

Animals↗
PubMed1976

Antimicrobial activities and antagonists of bacilysin and anticapsin.

The dipeptide antibiotic bacilysin is active against a wide range of bacteria and against Candida albicans. Its C-terminal amino acid, anticapsin, is a very poor antibacterial agent. The activities of both substances are strongly dependent on the nature of the culture medium. In a minimal medium the minimum inhibitory concentration for bacilysin with E. coli B is 10(-3) mug ml(-1). The action of bacilysin amino acids. With several bacteria, bacilysin-resistant mutants are found in unusually large numbers. It is suggested that peptide and amino acid transport systems play a role in these phenomena. The antimicrobial action of bacilysin is also inhibited by glucosamine and N-acetylglucosamine. This antibiotic may therefore interfere with glucosamine synthesis and thus with the synthesis of microbial cell walls.

Acetylglucosamine↗
PubMed2002

Shock structures and bunching fronts in excitable reaction-diffusion systems.

We report experimental results on the dynamics of excitation waves in a modified Belousov-Zhabotinsky reaction. The waves in this system obey nonmonotonic dispersion relations. This anomaly induces the stacking of excitation fronts into patterns with stable interpulse distances. The stacking process creates either a traveling shock structure or a cascade of bunching events in which metastable wave packets are formed. The direction and the speed of the shock are explained in terms of a simple geometrical analysis. We also present experimental evidence for the corresponding instabilities in two-dimensional systems. Here, wave stacking generates atypical structures in the collision of target patterns and wave bunching is accompanied by complex front deformations.

Cyclohexanones↗
PubMed2003

An isoleucine residue within the carboxyl-transferase domain of multidomain acetyl-coenzyme A carboxylase is a major determinant of sensitivity to aryloxyphenoxypropionate but not to cyclohexanedione inhibitors.

A 3,300-bp DNA fragment encoding the carboxyl-transferase domain of the multidomain, chloroplastic acetyl-coenzyme A carboxylase (ACCase) was sequenced in aryloxyphenoxypropionate (APP)-resistant and -sensitive Alopecurus myosuroides (Huds.). No resistant plant contained an Ile-1,781-Leu substitution, previously shown to confer resistance to APPs and cyclohexanediones (CHDs). Instead, an Ile-2,041-Asn substitution was found in resistant plants. Phylogenetic analysis of the sequences revealed that Asn-2,041 ACCase alleles derived from several distinct origins. Allele-specific polymerase chain reaction associated the presence of Asn-2,041 with seedling resistance to APPs but not to CHDs. ACCase enzyme assays confirmed that Asn-2,041 ACCase activity was moderately resistant to CHDs but highly resistant to APPs. Thus, the Ile-2,041-Asn substitution, which is located outside a domain previously shown to control sensitivity to APPs and CHDs in wheat (Triticum aestivum), is a direct cause of resistance to APPs only. In known multidomain ACCases, the position corresponding to the Ile/Asn-2,041 residue in A. myosuroides is occupied by an Ile or a Val residue. In Lolium rigidum (Gaud.), we found Ile-Asn and Ile-Val substitutions. The Ile-Val change did not confer resistance to the APP clodinafop, whereas the Ile-Asn change did. The position and the particular substitution at this position are of importance for sensitivity to APPs.

Acetyl-CoA Carboxylase↗
PubMed1995

Levels of a terpenoid glycoside (blumenin) and cell wall-bound phenolics in some cereal mycorrhizas.

Four cereals, Hordeum vulgare (barley), Triticum aestivum (wheat), Secale cereal (rye), and Avena sativa (oat), were grown in a defined nutritional medium with and without the arbuscular mycorrhizal fungus Glomus intraradices. Levels of soluble and cell wall-bound secondary metabolites in the roots of mycorrhizal and nonmycorrhizal plants were determined by high-performance liquid chromatography during the first 6 to 8 weeks of plant development. Whereas there was no difference in the levels of the cell wall-bound hydroxycinnamic acids, 4-coumaric and ferulic acids, there was a fungus-induced change of the soluble secondary root metabolites. The most obvious effect observed in all four cereals was the induced accumulation of a terpenoid glycoside. This compound was isolated and identified by spectroscopic methods (nuclear magnetic resonance, mass spectrometry) to be a cyclohexenone derivative, i.e. blumenol C 9-O-(2'-O-beta-glucuronosyl)-beta-glucoside. The level of this compound was found to be directly correlated with the degree of root colonization.

Avena↗
PubMed2003

The fungal metabolite austdiol.

The title compound, (7R,8S)-7,8-dihydroxy-3,7-dimethyl-6-oxo-7,8-dihydro-6H-isochromene-5-carbaldehyde, C(12)H(12)O(5), is a trans-vicinal diol. Of the two fused rings, which lie approximately in the same plane, the pyran ring is almost perfectly planar, while the cyclohexenone ring adopts a slightly distorted half-chair conformation. The crystal packing is dictated by two strong intermolecular O-H.O interactions, one involving hydroxy and keto groups, the other involving two hydroxy groups. Molecules are linked together through twofold axes, forming zigzag ribbons extended along the a axis.

Aldehydes↗
PubMed2004

2-(phenylaminomethylidene)cyclohexane-1,3-dione.

In the title compound, C(13)H(13)NO(2), there is polarization of pi-electron density from the amine N atom to the acceptor carbonyl groups: as a result, the molecule exists predominantly in an azomethino-1,3-diketone tautomeric form. There is crystallographic evidence that the phenyl ring, although roughly coplanar with the rest of the molecule, is deconjugated with the adjacent pi system of the molecule. The cyclohexane ring adopts an unsymmetrical half-chair conformation and converts between two inversion-related conformers. The molecule is stabilized by an intramolecular hydrogen bond, while the intermolecular packing is dominated by a number of short C-H.O contacts.

Aniline Compounds↗