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Tryptophan self-controls its synthesis

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Tryptophan (abbreviated as Trp ..

N2 - The heme of neuronal nitric-oxide synthase participates in oxygen activation but also binds self-generated NO during catalysis resulting in reversible feedback inhibition. We utilized point mutagenesis to investigate if a conserved tryptophan residue (Trp-409), which engages in π-stacking with the heme and hydrogen bonds to its axial cysteine ligand, helps control catalysis and regulation by NO. Surprisingly, routants W409F and W409Y were hyperactive compared with the wild type regarding NO synthesis without affecting cytochrome c reduction, reductase-independent N-hydroxyarginine oxidation, or Arg and tetrahydrobiopterin binding. In the absence of Arg, NADPH oxidation measurements showed that electron flux through the heine was actually slower in the Trp-409 routants than in wild-type nNOS. However, little or no NO complex accumulated during NO synthesis by the routants, as opposed to the wild type. This difference was potentially related to mutants forming unstable 6-coordinate ferrous-NO complexes under anaerobic conditions even in the presence of Arg and tetrahydrobiopterin. Thus, Trp-409 mutations minimize NO feedback inhibition by preventing buildup of an inactive ferrous- NO complex during the steady state. This overcomes the negative effect of the mutation on electron flux and results in hyperactivity. Conservation of Trp- 409 among different NOS suggests that the ability of this residue to regulate heme reduction and NO complex formation is important for enzyme physiologic function.

Tryptophan 409 controls the activity of ..

The heme of neuronal nitric-oxide synthase participates in oxygen activation but also binds self-generated NO during catalysis resulting in reversible feedback inhibition. We utilized point mutagenesis to investigate if a conserved tryptophan residue (Trp-409), which engages in π-stacking with the heme and hydrogen bonds to its axial cysteine ligand, helps control catalysis and regulation by NO. Surprisingly, routants W409F and W409Y were hyperactive compared with the wild type regarding NO synthesis without affecting cytochrome c reduction, reductase-independent N-hydroxyarginine oxidation, or Arg and tetrahydrobiopterin binding. In the absence of Arg, NADPH oxidation measurements showed that electron flux through the heine was actually slower in the Trp-409 routants than in wild-type nNOS. However, little or no NO complex accumulated during NO synthesis by the routants, as opposed to the wild type. This difference was potentially related to mutants forming unstable 6-coordinate ferrous-NO complexes under anaerobic conditions even in the presence of Arg and tetrahydrobiopterin. Thus, Trp-409 mutations minimize NO feedback inhibition by preventing buildup of an inactive ferrous- NO complex during the steady state. This overcomes the negative effect of the mutation on electron flux and results in hyperactivity. Conservation of Trp- 409 among different NOS suggests that the ability of this residue to regulate heme reduction and NO complex formation is important for enzyme physiologic function.

but also binds self-generated NO ..

"Tryptophan self-controls its synthesis." was asked by Shelly Notetaker on May 31 2017. 376 students have viewed the answer on StudySoup. View the answer on StudySoup.

Although serotonergic agonists may reduce rates of both externally directed and self-directed, aggression, there is debate concerning the relationship between these forms of aggression. Some investigators have contended that SIB can be viewed merely as redirected aggression. In support of this hypothesis, socially reared rhesus monkeys exhibit increases in rates of SIB when housed singly as adults., If a physical barrier thwarts an animal's attempt to reach a nearby conspecific, the motivation to aggress might be redirected inappropriately toward the aggressor itself. However, previous studies demonstrating an association between SIB and outward aggression did not control for the possibly confounding effects of stress level. When cortisol levels were equated between different experimental situations (that is, being alone or with a ‘stranger’), self-directed biting was not associated with outward aggression in rhesus monkeys. Although outward aggression varied according to the social context, rates of SIB were similar between types of stress level. This finding argues against the interpretation that SIB is simply a form of redirected aggression. In contrast, these findings are consistent with the view that SIB might represent a behavioral method of coping with periodic excessive levels of anxiety. In the present study, the tryptophan-induced suppression of cortisol levels in animals with SIB is an observation more consistent with the latter hypothesis. Our findings do not, however, refute the ‘redirected aggression’ hypothesis.

He then mailed to me a nasty little "progress note." A few days later my patient dropped by my office for a chat and pointed out that as a result of chelation therapy his blood pressure is down, his diabetes is under control, his arrhythmia is no longer present, and he has a new-found experience of well-being.

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A proximal tryptophan in NO synthase controls activity …

We utilized mutagenesis to investigate if a conserved tryptophan ..

N2 - The heme of neuronal nitric oxide synthase (nNOS) participates in O2 activation but also binds self-generated NO, resulting in reversible feedback inhibition. We utilized mutagenesis to investigate if a conserved tryptophan residue (Trp409), which engages in π-stacking with the heme and hydrogen bonds to its axial cysteine ligand, helps control catalysis and regulation by NO. Mutants W409F and W409Y were hyperactive regarding NO synthesis without affecting cytochrome c reduction, reductase-independent N-hydroxyarginine oxidation, or Arg and tetrahydrobiopterin binding. In the absence of Arg electron flux through the heme was slower in the W409 mutants than in wild-type. However, less NO complex accumulated during NO synthesis by the mutants. To understand the mechanism, we compared the kinetics of heme-NO complex formation, rate of heme reduction, kcat prior to and after NO complex formation, NO binding affinity, NO complex stability, and its reaction with O2. During the initial phase of NO synthesis, heme-NO complex formation was three and five times slower in W409F and W409Y, which corresponded to a slower heme reduction. NO complex formation inhibited wild-type turnover 7-fold but reduced mutant turnover less than 2-fold, giving mutants higher steady-state activities. NO binding kinetics were similar among mutants and wild type, although mutants also formed a 417 nm ferrous-NO complex. Oxidation of ferrous-NO complex was seven times faster in mutants than in wild type. We conclude that mutant hyperactivity primarily derives from slower heme reduction and faster oxidation of the heme-NO complex by O2. In this way Trp409 mutations minimize NO feedback inhibition by limiting buildup of the ferrous-NO complex during the steady state. Conservation of W409 among NOS suggests that this proximal Trp may regulate NO feedback inhibition and is important for enzyme physiologic function.

The heme of neuronal nitric oxide synthase (nNOS) participates in O2 activation but also binds self-generated NO, resulting in reversible feedback inhibition. We utilized mutagenesis to investigate if a conserved tryptophan residue (Trp409), which engages in π-stacking with the heme and hydrogen bonds to its axial cysteine ligand, helps control catalysis and regulation by NO. Mutants W409F and W409Y were hyperactive regarding NO synthesis without affecting cytochrome c reduction, reductase-independent N-hydroxyarginine oxidation, or Arg and tetrahydrobiopterin binding. In the absence of Arg electron flux through the heme was slower in the W409 mutants than in wild-type. However, less NO complex accumulated during NO synthesis by the mutants. To understand the mechanism, we compared the kinetics of heme-NO complex formation, rate of heme reduction, kcat prior to and after NO complex formation, NO binding affinity, NO complex stability, and its reaction with O2. During the initial phase of NO synthesis, heme-NO complex formation was three and five times slower in W409F and W409Y, which corresponded to a slower heme reduction. NO complex formation inhibited wild-type turnover 7-fold but reduced mutant turnover less than 2-fold, giving mutants higher steady-state activities. NO binding kinetics were similar among mutants and wild type, although mutants also formed a 417 nm ferrous-NO complex. Oxidation of ferrous-NO complex was seven times faster in mutants than in wild type. We conclude that mutant hyperactivity primarily derives from slower heme reduction and faster oxidation of the heme-NO complex by O2. In this way Trp409 mutations minimize NO feedback inhibition by limiting buildup of the ferrous-NO complex during the steady state. Conservation of W409 among NOS suggests that this proximal Trp may regulate NO feedback inhibition and is important for enzyme physiologic function.

regarding NO synthesis without ..
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    Tryptophan - Wikipedia

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Top 9 Health Benefits of Nicotinamide Riboside - …

AB - The heme of neuronal nitric oxide synthase (nNOS) participates in O2 activation but also binds self-generated NO, resulting in reversible feedback inhibition. We utilized mutagenesis to investigate if a conserved tryptophan residue (Trp409), which engages in π-stacking with the heme and hydrogen bonds to its axial cysteine ligand, helps control catalysis and regulation by NO. Mutants W409F and W409Y were hyperactive regarding NO synthesis without affecting cytochrome c reduction, reductase-independent N-hydroxyarginine oxidation, or Arg and tetrahydrobiopterin binding. In the absence of Arg electron flux through the heme was slower in the W409 mutants than in wild-type. However, less NO complex accumulated during NO synthesis by the mutants. To understand the mechanism, we compared the kinetics of heme-NO complex formation, rate of heme reduction, kcat prior to and after NO complex formation, NO binding affinity, NO complex stability, and its reaction with O2. During the initial phase of NO synthesis, heme-NO complex formation was three and five times slower in W409F and W409Y, which corresponded to a slower heme reduction. NO complex formation inhibited wild-type turnover 7-fold but reduced mutant turnover less than 2-fold, giving mutants higher steady-state activities. NO binding kinetics were similar among mutants and wild type, although mutants also formed a 417 nm ferrous-NO complex. Oxidation of ferrous-NO complex was seven times faster in mutants than in wild type. We conclude that mutant hyperactivity primarily derives from slower heme reduction and faster oxidation of the heme-NO complex by O2. In this way Trp409 mutations minimize NO feedback inhibition by limiting buildup of the ferrous-NO complex during the steady state. Conservation of W409 among NOS suggests that this proximal Trp may regulate NO feedback inhibition and is important for enzyme physiologic function.

Creatine Supplement - Unbiased Review on Usage, …

1. In living cells there are hundreds of different enzymes working together in a coordinated manner, and since cells neither synthesize nor break down more material than is required for normal metabolism and growth, precise enzyme regulation is required for turning metabolic reactions on and off.
2. There is tremendous diversity in the mechanisms bacteria use to regulate enzyme synthesis and enzyme activity.
3. Ways in which enzymes can be controlled or regulated iinclude controlling the synthesis of the enzyme (genetic control) and controlling the activity of the enzyme (feedback inhibition).
4. In prokaryotes, genetic control of enzyme activity includes the induction or repression of enzyme synthesis by regulatory proteins that can bind to DNA and either block or enhance the function of RNA polymerase, the enzyme required for transcription.
5. An operon is a set of genes collectively controlled by a regulatory protein.
6. Regulatory proteins may function either as repressors or activators.
7. Repressors are regulatory proteins that block transcription of mRNA by preventing RNA polymerase from transcribing the coding sequence for the enzymes.
8. Some repressors, as in the case of the trp operon, are synthesized in a form that cannot by itself bind to the operator. This is referred to as a repressible system. The binding of a molecule called a corepressor, however, alters the shape of the regulatory protein to a form that can bind to the operator and subsequently block transcription.
9. Some repressors, as in the case of the lac operon, are synthesized in a form that readily binds to the operator and blocks transcription. However, the binding of a molecule called an inducer alters the shape of the regulatory protein in a way that now blocks its binding to the operator and thus permits transcription. This is referred to as an inducible system.
10. Activators are regulatory proteins that promote transcription of mRNA by enabling RNA polymerase to transcribing the coding sequence for the enzymes.
11. Enhancers are regulatory proteins that bind to DNA located some distance from the operon they control by working with DNA-bending proteins. The DNA-bending proteins bend the DNA in a way that now allows the enhancer to interact with the promoter in such a way that RNA polymerase can now bind and initiate transcription
12. Bacteria also use translational control of enzyme synthesis. One method is for the bacteria to produce noncoding RNA (ncRNA) molecules that are complementary to the mRNA coding for the enzyme, and when the small RNA binds to the mRNA by complementary base pairing, ribosomes cannot attach to the mRNA, the mRNA is not transcribed and translated into protein, and the enzyme is not made. In bacteria, these ncRNAs are often called small RNAs (sRNAs).
13. Feedback inhibition controls the activity of the enzyme rather than its synthesis and can be noncompetitive or competitive.
14. In the case of non-competitive inhibition, the inhibitor is the end product of a metabolic pathway that is able to bind the allosteric site on the enzyme. Binding of the inhibitor to the allosteric site alters the shape of the enzyme's active site thus preventing binding of the first substrate in the metabolic pathway. In this way, the pathway is turned off.
15. In the case of what is called competitive inhibition, the inhibitor is the end product of an enzymatic reaction. That end product is also capable of reacting with the enzyme's active site and prevents the enzyme from binding its normal substrate. As a result, the end product is no longer synthesized.

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