3-Phosphoshikimate 1-Carboxyvinyltransferase
Alkyl and Aryl Transferases
Encyclopedias as Topic
Angiotensin-Converting Enzyme Inhibitors
Substrate Specificity
HIV Protease Inhibitors
Ritonavir
Enzymes
Molecular cloning and sequencing of the aroA gene from Actinobacillus pleuropneumoniae and its use in a PCR assay for rapid identification. (1/105)
The gene (aroA) of Actinobacillus pleuropneumoniae, serotype 2, encoding 5-enolpyruvylshikimate-3-phosphate synthase was cloned by complementation of the aroA mutation in Escherichia coli K-12 strain AB2829, and the nucleotide sequence was determined. A pair of primers from the 5' and 3' termini were selected to be the basis for development of a specific PCR assay. A DNA fragment of 1,025 bp was amplified from lysed A. pleuropneumoniae serotypes 1 to 12 of biovar 1 or from isolated DNA. No PCR products were detected when chromosomal DNAs from other genera were used as target DNAs; however, a 1,025-bp DNA fragment was amplified when Actinobacillus equuli chromosomal DNA was used as a target, which could be easily differentiated by its NAD independence. The PCR assay developed was very sensitive, with lower detection limits of 12 CFU with A. pleuropneumoniae cells and 0.8 pg with extracted DNA. Specificity and sensitivity make this PCR assay a useful method for the rapid identification and diagnosis of A. pleuropneumoniae infections. (+info)Evaluation of Salmonella typhimurium mutants in a model of experimental gastroenteritis. (2/105)
Salmonella typhimurium strains harboring independent, defined mutations in aroA, invA, ssrA, or msbB were assessed for their ability to induce fluid accumulation, tissue damage, and local inflammation in rabbit ileal loops. Three wild-type strains of S. typhimurium, TML, HWSH, and SL1344, and two mutant strains, S. typhimurium SL1344 ssrA and S. typhimurium SL1344 msbB, consistently induced fluid accumulation in the lumen of loops and inflammation of loop-associated tissues. In contrast, three different S. typhimurium aroA strains and an invA mutant of SL1344 did not induce significant fluid accumulation in the rabbit ileal loops. However, the S. typhimurium aroA strains did induce an inflammatory infiltrate and some local villus-associated damage, but the invA mutant did not. Histologically, wild-type S. typhimurium, S. typhimurium SL1344 ssrA, and S. typhimurium SL1344 msbB demonstrated more severe effects on villus architecture than S. typhimurium aroA strains, whereas S. typhimurium invA-infected loops showed no detectable damage. This suggests that villus damage most likely contributes to fluid accumulation within the loop. (+info)Characterization of Streptococcus pneumoniae 5-enolpyruvylshikimate 3-phosphate synthase and its activation by univalent cations. (3/105)
The aroA gene (Escherichia coli nomenclature) encoding 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase from the gram-positive pathogen Streptococcus pneumoniae has been identified, cloned and overexpressed in E. coli, and the enzyme purified to homogeneity. It was shown to catalyze a reversible conversion of shikimate 3-phosphate (S3P) and phosphoenolpyruvate (PEP) to EPSP and inorganic phosphate. Activation by univalent cations was observed in the forward reaction, with NH+4, Rb+ and K+ exerting the greatest effects. Km(PEP) was lowered by increasing [NH+4] and [K+], whereas Km(S3P) rose with increasing [K+], but fell with increasing [NH+4]. Increasing [NH+4] and [K+] resulted in an overall increase in kcat. Glyphosate (GLP) was found to be a competitive inhibitor with PEP, but the potency of inhibition was profoundly affected by [NH+4] and [K+]. For example, increasing [NH+4] and [K+] reduced Ki(GLP versus PEP) up to 600-fold. In the reverse reaction, the enzyme catalysis was less sensitive to univalent cations. Our analysis included univalent cation concentrations comparable with those found in bacterial cells. Therefore, the observed effects of these metal ions are more likely to reflect the physiological behavior of EPSP synthase and also add to our understanding of how to inhibit this enzyme in the host organism. As there is a much evidence to suggest that EPSP synthase is essential for bacterial survival, its discovery in the serious gram-positive pathogen S. pneumoniae and its inhibition by GLP indicate its potential as a broad-spectrum antibacterial target. (+info)Extending the CD4(+) T-cell epitope specificity of the Th1 immune response to an antigen using a Salmonella enterica serovar typhimurium delivery vehicle. (4/105)
We analyzed the CD4 T-cell immunodominance of the response to a model antigen (Ag), MalE, when delivered by an attenuated strain of Salmonella enterica serovar Typhimurium (SL3261*pMalE). Compared to purified MalE Ag administered with adjuvant, the mapping of the peptide-specific proliferative responses showed qualitative differences when we used the Salmonella vehicle. We observed the disappearance of one out of eight MalE peptides' T-cell reactivity upon SL3261*pMalE immunization, but this phenomenon was probably due to a low level of T-cell priming, since it could be overcome by further immunization. The most striking effect of SL3261*pMalE administration was the activation and stimulation of new MalE peptide-specific T-cell responses that were silent after administration of purified Ag with adjuvant. Ag presentation assays performed with MalE-specific T-cell hybridomas showed that infection of Ag-presenting cells by this intracellular attenuated bacterium did not affect the processing and presentation of the different MalE peptides by major histocompatibility complex (MHC) class II molecules and therefore did not account for immunodominance modulation. Thus, immunodominance of the T-cell response to microorganisms is governed not only by the frequency of the available T-cell repertoire or the processing steps in Ag-presenting cells that lead to MHC presentation but also by other parameters probably related to the infectious process and to the bacterial products. Our results indicate that, upon infection by a microorganism, the specificity of the T-cell response induced against its Ags can be much more effective than with purified Ags and that it cannot completely be mimicked by purified Ags administered with adjuvant. (+info)Comparison of abilities of Salmonella enterica serovar typhimurium aroA aroD and aroA htrA mutants to act as live vectors. (5/105)
We compared the ability of Salmonella enterica serovar Typhimurium SL1344 aroA aroD (BRD509) and aroA htrA (BRD807) mutants to act as live vectors for delivery of fragment C of tetanus toxin (FrgC). FrgC was expressed in these strains from either pTETnir15 or pTEThtrA1. BRD509FrgC(+) strains elicited approximately 2-log-higher serum anti-FrgC antibody titers than BRD807FrgC(+) strains. All mice immunized with BRD807pTEThtrA1, BRD509pTEThtrA1, and BRD509pTETnir15 (but not BRD807pTETnir15) were protected against tetanus. (+info)Interaction of the herbicide glyphosate with its target enzyme 5-enolpyruvylshikimate 3-phosphate synthase in atomic detail. (6/105)
Biosynthesis of aromatic amino acids in plants, many bacteria, and microbes relies on the enzyme 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase, a prime target for drugs and herbicides. We have identified the interaction of EPSP synthase with one of its two substrates (shikimate 3-phosphate) and with the widely used herbicide glyphosate by x-ray crystallography. The two-domain enzyme closes on ligand binding, thereby forming the active site in the interdomain cleft. Glyphosate appears to occupy the binding site of the second substrate of EPSP synthase (phosphoenol pyruvate), mimicking an intermediate state of the ternary enzyme.substrates complex. The elucidation of the active site of EPSP synthase and especially of the binding pattern of glyphosate provides a valuable roadmap for engineering new herbicides and herbicide-resistant crops, as well as new antibiotic and antiparasitic drugs. (+info)Genetic background of attenuated Salmonella typhimurium has profound influence on infection and cytokine patterns in human dendritic cells. (7/105)
Salmonella typhimurium (ST) can cause infection in man, and attenuated strains are under consideration as live vaccine vectors. However, little is known about the interaction of ST with human dendritic cells (DC). Here, we compared the consequences of exposure of human, monocyte-derived DC with different attenuated strains of ST. Infection was observed with all four strains tested (wild type, PhoP-, PhoPc, and AroA), but the PhoPc strain was by far the most efficient. Intracellular persistence of wild type and PhoP- was longer than that of PhoPc and AroA, both of which were largely eliminated within 24 h. Most DC survived infection by the attenuated strains, although apoptosis was observed in a fraction of the exposed cells. All strains induced DC maturation, independent from the extent of infection. Although all strains stimulated secretion of TNF-alpha and IL-12 strongly, PhoPc induced significantly less IL-10 than the other three strains and as much as 10 times less IL-10 than heat-killed PhoPc, suggesting that this mutant suppressed the secretion of IL-10 by the DC. These data indicate that infectivity, bacterial elimination, and cytokine secretion in human DC are controlled by the genetic background of ST. (+info)Chemical shift mapping of shikimate-3-phosphate binding to the isolated N-terminal domain of 5-enolpyruvylshikimate-3-phosphate synthase. (8/105)
To facilitate evaluation of enzyme-ligand complexes in solution, we have isolated the 26-kDa N-terminal domain of 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase for analysis by NMR spectroscopy. The isolated domain is capable of binding the substrate shikimate-3-phosphate (S3P), and this letter reports the localization of the S3P binding site using chemical shift mapping. Based on the NMR data, we propose that Ser23, Arg27, Ser197, and Tyr200 are directly involved in S3P binding. We also describe changes in the observed nuclear Overhauser effects (NOEs) that are consistent with a partial conformational change in the N-terminal domain upon S3P binding. (+info)3-Phosphoshikimate 1-Carboxyvinyltransferase (PCT) is an enzyme that catalyzes the sixth step in the biosynthesis of aromatic amino acids in plants and microorganisms. The reaction it catalyzes is the conversion of 3-phosphoshikimate (3PSM) and phosphoenolpyruvate (PEP) to 5-enolpyruvylshikimate-3-phosphate (EPSP). This step is a key control point in the aromatic amino acid biosynthetic pathway, and the enzyme is the target of several herbicides, including glyphosate. The gene that encodes this enzyme is also used as a molecular marker for plant systematics and evolutionary studies.
Alkyl and aryl transferases are a group of enzymes that catalyze the transfer of alkyl or aryl groups from one molecule to another. These enzymes play a role in various biological processes, including the metabolism of drugs and other xenobiotics, as well as the biosynthesis of certain natural compounds.
Alkyl transferases typically catalyze the transfer of methyl or ethyl groups, while aryl transferases transfer larger aromatic rings. These enzymes often use cofactors such as S-adenosylmethionine (SAM) or acetyl-CoA to donate the alkyl or aryl group to a recipient molecule.
Examples of alkyl and aryl transferases include:
1. Methyltransferases: enzymes that transfer methyl groups from SAM to various acceptor molecules, such as DNA, RNA, proteins, and small molecules.
2. Histone methyltransferases: enzymes that methylate specific residues on histone proteins, which can affect chromatin structure and gene expression.
3. N-acyltransferases: enzymes that transfer acetyl or other acyl groups to amino groups in proteins or small molecules.
4. O-acyltransferases: enzymes that transfer acyl groups to hydroxyl groups in lipids, steroids, and other molecules.
5. Arylsulfatases: enzymes that remove sulfate groups from aromatic rings, releasing an alcohol and sulfate.
6. Glutathione S-transferases (GSTs): enzymes that transfer the tripeptide glutathione to electrophilic centers in xenobiotics and endogenous compounds, facilitating their detoxification and excretion.
An encyclopedia is a comprehensive reference work containing articles on various topics, usually arranged in alphabetical order. In the context of medicine, a medical encyclopedia is a collection of articles that provide information about a wide range of medical topics, including diseases and conditions, treatments, tests, procedures, and anatomy and physiology. Medical encyclopedias may be published in print or electronic formats and are often used as a starting point for researching medical topics. They can provide reliable and accurate information on medical subjects, making them useful resources for healthcare professionals, students, and patients alike. Some well-known examples of medical encyclopedias include the Merck Manual and the Stedman's Medical Dictionary.
Angiotensin-Converting Enzyme (ACE) inhibitors are a class of medications that are commonly used to treat various cardiovascular conditions, such as hypertension (high blood pressure), heart failure, and diabetic nephropathy (kidney damage in people with diabetes).
ACE inhibitors work by blocking the action of angiotensin-converting enzyme, an enzyme that converts the hormone angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor, meaning it narrows blood vessels and increases blood pressure. By inhibiting the conversion of angiotensin I to angiotensin II, ACE inhibitors cause blood vessels to relax and widen, which lowers blood pressure and reduces the workload on the heart.
Some examples of ACE inhibitors include captopril, enalapril, lisinopril, ramipril, and fosinopril. These medications are generally well-tolerated, but they can cause side effects such as cough, dizziness, headache, and elevated potassium levels in the blood. It is important for patients to follow their healthcare provider's instructions carefully when taking ACE inhibitors and to report any unusual symptoms or side effects promptly.
Substrate specificity in the context of medical biochemistry and enzymology refers to the ability of an enzyme to selectively bind and catalyze a chemical reaction with a particular substrate (or a group of similar substrates) while discriminating against other molecules that are not substrates. This specificity arises from the three-dimensional structure of the enzyme, which has evolved to match the shape, charge distribution, and functional groups of its physiological substrate(s).
Substrate specificity is a fundamental property of enzymes that enables them to carry out highly selective chemical transformations in the complex cellular environment. The active site of an enzyme, where the catalysis takes place, has a unique conformation that complements the shape and charge distribution of its substrate(s). This ensures efficient recognition, binding, and conversion of the substrate into the desired product while minimizing unwanted side reactions with other molecules.
Substrate specificity can be categorized as:
1. Absolute specificity: An enzyme that can only act on a single substrate or a very narrow group of structurally related substrates, showing no activity towards any other molecule.
2. Group specificity: An enzyme that prefers to act on a particular functional group or class of compounds but can still accommodate minor structural variations within the substrate.
3. Broad or promiscuous specificity: An enzyme that can act on a wide range of structurally diverse substrates, albeit with varying catalytic efficiencies.
Understanding substrate specificity is crucial for elucidating enzymatic mechanisms, designing drugs that target specific enzymes or pathways, and developing biotechnological applications that rely on the controlled manipulation of enzyme activities.
HIV Protease Inhibitors are a class of antiretroviral medications used in the treatment of HIV infection. They work by blocking the activity of the HIV protease enzyme, which is necessary for the virus to replicate and infect new cells. By inhibiting this enzyme, the medication prevents the virus from maturing and assembling into new infectious particles.
HIV protease inhibitors are often used in combination with other antiretroviral drugs as part of a highly active antiretroviral therapy (HAART) regimen. This approach has been shown to effectively suppress viral replication, reduce the amount of virus in the bloodstream (viral load), and improve the health and longevity of people living with HIV.
Examples of HIV protease inhibitors include saquinavir, ritonavir, indinavir, nelfinavir, amprenavir, fosamprenavir, atazanavir, darunavir, and tipranavir. These medications are usually taken orally in the form of tablets or capsules, and may be prescribed alone or in combination with other antiretroviral drugs.
It is important to note that HIV protease inhibitors can have significant side effects, including gastrointestinal symptoms such as nausea, diarrhea, and abdominal pain, as well as metabolic changes such as increased cholesterol and triglyceride levels. Therefore, regular monitoring of liver function, lipid levels, and other health parameters is necessary to ensure safe and effective use of these medications.
Ritonavir is an antiretroviral medication used in the treatment and prevention of HIV/AIDS. It is a protease inhibitor, which works by blocking the action of protease, an enzyme that the virus needs to multiply. By doing this, Ritonavir helps to reduce the amount of HIV in the body, keeping it at a low level and preventing the disease from progressing.
Ritonavir is often used in combination with other antiretroviral drugs as part of highly active antiretroviral therapy (HAART). It is also sometimes used at lower doses to boost the levels of other protease inhibitors in the body, a practice known as "pharmacologic boosting."
It's important to note that Ritonavir does not cure HIV/AIDS, but it can help people with HIV live longer, healthier lives. As with all medications, Ritonavir can have side effects, and it may interact with other drugs, so it's important to take it exactly as prescribed by a healthcare provider.
Enzymes are complex proteins that act as catalysts to speed up chemical reactions in the body. They help to lower activation energy required for reactions to occur, thereby enabling the reaction to happen faster and at lower temperatures. Enzymes work by binding to specific molecules, called substrates, and converting them into different molecules, called products. This process is known as catalysis.
Enzymes are highly specific and will only catalyze one particular reaction with a specific substrate. The shape of the enzyme's active site, where the substrate binds, determines this specificity. Enzymes can be regulated by various factors such as temperature, pH, and the presence of inhibitors or activators. They play a crucial role in many biological processes, including digestion, metabolism, and DNA replication.
In the context of medicine and pharmacology, "kinetics" refers to the study of how a drug moves throughout the body, including its absorption, distribution, metabolism, and excretion (often abbreviated as ADME). This field is called "pharmacokinetics."
1. Absorption: This is the process of a drug moving from its site of administration into the bloodstream. Factors such as the route of administration (e.g., oral, intravenous, etc.), formulation, and individual physiological differences can affect absorption.
2. Distribution: Once a drug is in the bloodstream, it gets distributed throughout the body to various tissues and organs. This process is influenced by factors like blood flow, protein binding, and lipid solubility of the drug.
3. Metabolism: Drugs are often chemically modified in the body, typically in the liver, through processes known as metabolism. These changes can lead to the formation of active or inactive metabolites, which may then be further distributed, excreted, or undergo additional metabolic transformations.
4. Excretion: This is the process by which drugs and their metabolites are eliminated from the body, primarily through the kidneys (urine) and the liver (bile).
Understanding the kinetics of a drug is crucial for determining its optimal dosing regimen, potential interactions with other medications or foods, and any necessary adjustments for special populations like pediatric or geriatric patients, or those with impaired renal or hepatic function.