Call us toll-free

Quick academic help

Don't let the stress of school get you down! Have your essay written by a professional writer before the deadline arrives.

Calculate the price

Pages:

275 Words

$19,50

An enzyme catalyzing the synthesis of a specific substance.

Histidine is special in that its biosynthesis is inherently linked to thepathways of nucleotide formation. Histidine residues are often found in enzymeactive sites, where the chemistry of the imidazole ring of histidine makes it anucleophile and a good acid/base catalyzer. We now know that RNA can havecatalytic properties, and there has been speculation that life was originallyRNA-based. Perhaps the transition to protein catalysis from RNA catalysisoccurred at the origin of histidine biosynthesis.

Immobilized lipase catalyzing glucose stearate synthesis and their surfactant properties analysis.

We will see THF again when we study the synthesis of thymidylate from dUMP,catalyzed by the enzyme inwhich N5,N10-methylene-THF is the methyl donor.

Bile Acid Synthesis, Metabolism and Biological Functions

21/12/2017 · View This Abstract Online; Bioengineering of bacterial polymer inclusions catalyzing the synthesis of N-acetylneuraminic acid. Appl Environ Microbiol.

N2 - Biotin synthesis in Escherichia coli requires the functions of the bioH and bioC genes to synthesize the precursor pimelate moiety by use of a modified fatty acid biosynthesis pathway. However, it was previously noted that bioH has been replaced with bioG or bioK within the biotin synthetic gene clusters of other bacteria. We report that each of four BioG proteins from diverse bacteria and two cyanobacterial BioK proteins functionally replace E. coli BioH in vivo. Moreover, purified BioG proteins have esterase activity against pimeloyl-ACP methyl ester, the physiological substrate of BioH. Two of the BioG proteins block biotin synthesis when highly expressed and these toxic proteins were shown to have more promiscuous substrate specificities than the non-toxic BioG proteins. A postulated BioG-BioC fusion protein was shown to functionally replace both the BioH and BioC functions of E. coli. Although the BioH, BioG and BioK esterases catalyze a common reaction, the proteins are evolutionarily distinct.

AB - Biotin synthesis in Escherichia coli requires the functions of the bioH and bioC genes to synthesize the precursor pimelate moiety by use of a modified fatty acid biosynthesis pathway. However, it was previously noted that bioH has been replaced with bioG or bioK within the biotin synthetic gene clusters of other bacteria. We report that each of four BioG proteins from diverse bacteria and two cyanobacterial BioK proteins functionally replace E. coli BioH in vivo. Moreover, purified BioG proteins have esterase activity against pimeloyl-ACP methyl ester, the physiological substrate of BioH. Two of the BioG proteins block biotin synthesis when highly expressed and these toxic proteins were shown to have more promiscuous substrate specificities than the non-toxic BioG proteins. A postulated BioG-BioC fusion protein was shown to functionally replace both the BioH and BioC functions of E. coli. Although the BioH, BioG and BioK esterases catalyze a common reaction, the proteins are evolutionarily distinct.

Bile Acid Synthesis and Utilization

Frontiers Rhodotorula glutinis Phenylalanine/Tyrosine Ammonia Lyase Enzyme Catalyzed Synthesis of the Methyl Ester of para-Hydro

ATP synthesis catalyzed by ATP synthase is powered bythe transmembrane electrochemical proton potential difference, composed of twocomponents: the chemical and theelectrical one. The more protons are on one side of a membrane relativetothe other, the higher is the driving force for a proton to cross themembrane. As proton is a charged particle, its movement is alsoinfluenced by electrical field: transmembrane electrical potentialdifference will drive protons from positively charged side tothe negatively charged one.

ATP synthesis catalyzed by ATP synthase is powered bythe transmembrane electrochemical proton potential difference, composed of twocomponents: the chemical and theelectrical one. The more protons are on one side of a membrane relativetothe other, the higher is the driving force for a proton to cross themembrane. As proton is a charged particle, its movement is alsoinfluenced by electrical field: transmembrane electrical potentialdifference will drive protons from positively charged side tothe negatively charged one. A water mill is a good analogy: the difference between the water levelsbefore and after the dam provides potential energy; downhill water flowrotates thewheel; the rotation is used to perform some work (ATP synthesis in ourcase). Quantitatively is measured in Joules per mole (J mol-1) and isdefined as:
where the "" and "" indices denote the ositively and the egatively charged sides of thecoupling membrane; is Faraday constant(96 485 C mol-1); is the molar gas constant(8.314 J mol-1K-1), is the temperature in Kelvins, and is thetransmembrane electrical potential difference involts. The value of tells, how much energy is required (or is released, depending on thedirection of the transmembrane proton flow) to move 1 mol of protonsacross the membrane.
It is often more convenient to use not , but protonmotive force ():

At room temperature (25oC) the protonmotive force (inmillivolts, as well as )is:
In the absence of transmembrane pH difference equals the transmembraneelectrical potential difference and can be directly measured by severalexperimental techniques (i.e. permeate ion distribution,potential-sensitive dyes, electrochromic carotenoid bandshift, etc.).Each pH unit of the transmembrane pH gradient corresponds to 59 mVof .
For most biological membranes engaged in ATP synthesis the value lies between 120 and 200mV ( between 11.6 and19.3 kJ mol-1).
The catalytic mechanism of ATP synthasemost probably involves rotation of Gamma subunit together with subunitEpsilon and -subunitoligomer relative to the rest of the enzyme. Such rotation wasexperimentally shown for ATP hydrolysis uncoupled to protontranslocation. Moreover, recent experiments revealed, that if Gammasubunit is mechanically forced into rotation, ATP synthesis takes placeeven without proton-translocating FO-portion.
It seems most probable that such rotation takes place . However, there is nodirect experimental evidence for such rotary mechanism in the intactenzyme under physiological conditions.
The proposed mechanism is the following:
ATP synthase activity is specifically inhibited by several compounds(both organic and inorganic). Most of these inhibitors are very toxic, so great careand appropriate safety precautions are essential when working with them (it is not very surprising thatwe get unhappy when OUR ATP synthase is blocked!).Most inhibitors are specific for either proton-translocating FO-portion, or hydrophilicF1-portion, so the section below is divided accordingly. Oligomycin is the inhibitor that gave the name "FO" to the membrane-embedded portion of ATP synthase. The subscript letter "O" in FO(not zero!) comes from Oligomycin sensitivity of this hydrophobicphosphorylation Factor in mitochondria.
Oligomycin binds on theinterface of subunit and -ring oligomer and blocks the rotary proton translocation in FO. If the enzyme is well-coupled, the activity of F1is also blocked. Because of the latter phenomenon, a subunit of mitochondrial F1-portionthat connects F1 with FO was named Oligomycin-Sensitivity Conferring Protein (OSCP).This subunit is essential for good coupling between F1 and FO and makes the ATPase activity of F1 sensitive to FO inhibitor oligomycin, hence the name.
Oligomycin is specific for mitochondrial ATP synthase and in micromolar concentrationseffectively blocks proton transport through FO. This inhibitor also works in some bacterial enzymes that show highsimilarity to mitochondrial ATP synthase, e.g. enzyme from purple bacterium . But ATP synthase from chloroplasts and from most bacteria (including )has low sensitivity to oligomycin.
It should also be noted that oligomycin in high concentrations also affects the activity of mitochondrial F1. DCCD (abbreviation for Dicyclohexylcarbodiimide; also known as DCC, as N,N'-dicyclohexylcarbodiimide, as Bis(cyclohexyl)carbodiimide, and as 1,3-dicyclohexylcarbodiimide) is a small organic molecule thatcan covalently modify protonated carboxyl groups. When added to ATP synthase at pH above 8, DCCD almost exclusively reacts with the carboxyl group of the conserved acidic amino acid residue of subunit (that is why subunit is sometimes called "DCCD-binding protein"). that has elevated pK and can therefore be protonated at such a high pH. Modification of the carboxyl group in a single -subunit is enough to renderthe whole -ring oligomer inactive. Because DCCD covalently binds to -subunit,this inhibition is irreversible.
The carboxyl group of the conserved amino acid residue in subunit -subunit is present inall ATP synthases known so far. So DCCD is a universal inhibitor that can FO function in bacterial, mitochondrial and chloroplast enzymes. Moreover, V- and A-type proton-transporting ATPasesare also sensitive to DCCD for the same reason. Sodium-transporting ATP synthases are also effectively inhibited by DCCD.
At lower pH (1 and inactivates it. So this compound canbe considered as an inhibitor of both FO and F1. However, inhibition of FOis highly specific, well-defined, and requires much lower DCCD concentration so usually thisinhibitor is used as FO-specific.

Download: Discovery and biochemical characterization of a mannose Phosphorylase catalyzing the synthesis of novel 13 Mannosides
Order now
  • UNMATCHED QUALITY

    As soon as we have completed your work, it will be proofread and given a thorough scan for plagiarism.

  • STRICT PRIVACY

    Our clients' personal information is kept confidential, so rest assured that no one will find out about our cooperation.

  • COMPLETE ORIGINALITY

    We write everything from scratch. You'll be sure to receive a plagiarism-free paper every time you place an order.

  • ON-TIME DELIVERY

    We will complete your paper on time, giving you total peace of mind with every assignment you entrust us with.

  • FREE CORRECTIONS

    Want something changed in your paper? Request as many revisions as you want until you're completely satisfied with the outcome.

  • 24/7 SUPPORT

    We're always here to help you solve any possible issue. Feel free to give us a call or write a message in chat.

Order now

The end products of cholesterol utilization are the bile acids

Aspartate is transaminated to asparagine in an ATP-dependent reactioncatalyzed by asparagine synthetase, and glutamine is the amino group donor:

Glossary | Linus Pauling Institute | Oregon State University

The enzyme is also regulated by covalent modification (adenylylation of a Tyrresidue), which results in an increase sensitivity to the cumulative feedbackinhibition by the above nine effectors. Adenylyltransferase is the enzyme whichcatalyzes both the adenylylation and deadenylylation of E. coli glutaminesynthetase, and this enzyme is complexed with a tetrameric regulatory protein, PII.Regulation of the adenylylation and its reverse occurs at the level of PII,depending upon the uridylylation of another Tyr residue, located on PII.When PII is uridylylated, glutamine synthetase is deadenylylated; thereverse occurs when UMP is covalently attached to the Tyr residue of PII.The level of uridylylation is, in turn, regulated by the activities of the twoenzymes, uridylyltransferase and uridylyl-removing enzyme, both located on thesame protein. Uridylyltransferase is activated by -ketoglutarateand ATP, while it is inhibited by glutamine and Pi.

Sulfide synthesis by S-alkylation or 1,4-addition

The first committed step for the synthesis of Lys, Met and Thr is the firststep, in which aspartate is phosphorylated to aspartyl--phosphate,catalyzed by :

Order now
  • You submit your order instructions

  • We assign an appropriate expert

  • The expert takes care of your task

  • We send it to you upon completion

Order now
  • 37 684

    Delivered orders

  • 763

    Professional writers

  • 311

    Writers online

  • 4.8/5

    Average quality score

Order now
  • Kim

    "I have always been impressed by the quick turnaround and your thoroughness. Easily the most professional essay writing service on the web."

  • Paul

    "Your assistance and the first class service is much appreciated. My essay reads so well and without your help I'm sure I would have been marked down again on grammar and syntax."

  • Ellen

    "Thanks again for your excellent work with my assignments. No doubts you're true experts at what you do and very approachable."

  • Joyce

    "Very professional, cheap and friendly service. Thanks for writing two important essays for me, I wouldn't have written it myself because of the tight deadline."

  • Albert

    "Thanks for your cautious eye, attention to detail and overall superb service. Thanks to you, now I am confident that I can submit my term paper on time."

  • Mary

    "Thank you for the GREAT work you have done. Just wanted to tell that I'm very happy with my essay and will get back with more assignments soon."

Ready to tackle your homework?

Place an order