https://sci-hub.do/10.1111/j.1432-1033.1989.tb14635.x
>Salmon liver was chosen for the isolation of 6-pyruvoyl tetrahydropterin synthase, one of the enzymes involved in tetrahydrobiopterin biosynthesis. A 9500-fold purification was obtained and the purified enzyme showed two single bands of 16 and 17 kDa on SDS/PAGE. The native enzyme (68 kDa) consists of four subunits and needs free thiol groups for enzymatic activity as was shown by reacting the enzyme with the fluorescent thiol reagent N-(7-dimethylamino-4-methylcoumarinyl)-maleimide. The enzyme is heat-stable up to 80 “C, has an isoelectric point of 6.0-6.3, and a pH optimum at 7.5. The enzyme is Mg2+-dependent and has a Michaelis constant for its substrate dihydroneopterin triphosphate of 2.2 pM. The turnover number of the purified salmon liver enzyme is about 50 times as high as that of the enzyme purified from human liver. It does not bind to the lectin concanavalin A, indicating that it is free of mannose and glucose residues. Polyclonal antibodies raised against the purified enzyme in Balb/c mice were able to immunoprecipitate enzyme activity. The same polyclonal serum was not able to immunoprecipitate enzyme activity of human liver 6-pyruvoyl tetrahydropterin synthase, nor was any cross-reaction in ELISA tests seen.
https://en.wikipedia.org/wiki/6-Pyruvoyltetrahydropterin_synthase
This is regarding that bh4 theory
EDIT:
more:
TETRAHYDROBIOPTERIN-PRODUCING ENZYME ACTIVITIES IN LIVER OF ANIMALS AND MAN*
>In order to find animal species with high activitie s of the enzymes involved in the biosynthesis of tetrahydrobiopterin (BH4), GTP cyclohydrolase I (GTPCH), 6-pyruvoyl-tetrahydropterin synthase (PTS), sepiapterin reductase (SR), dihydropteridine reductase (DHPR) and total pterins were measured in the liver s of man, monkey, pig, dog, rat, rabbit, sheep, cattle, horse, chicken and trout. Duch et al. (1) have measured the GTPCH activitie s in different tissues of monkey, dog and mouse. Their results show that the live r seems in fact to be the organ of choice to look for the enzymes involved in BH4 biosynthesis
A new architecture for iterative Type I polyketide synthases (PKS) from fungi has been investigated. TerA is a canonical non‐reducing PKS which interacts with TerB, a fragment of a highly reducing PKS containing a functional ketoreductase. Interaction appears to be mediated between a non‐functional dehydratase domain of TerB and the TerA product template domain. Working together, TerAB synthesises 6‐hydroxymellein, a precursor of terrein and other fungal metabolites.
Abstract
The polyketide synthase (PKS)‐like protein TerB, consisting of inactive dehydratase, inactive C‐methyltransferase, and functional ketoreductase domains collaborates with the iterative non reducing PKS TerA to produce 6‐hydroxymellein, a key pathway intermediate during the biosynthesis of various fungal natural products. The catalytically inactive dehydratase domain of TerB appears to mediate productive interactions with TerA, demonstrating a new mode of trans‐interaction between iterative PKS components.
https://ift.tt/321Xu2S
A new diterpene synthase (CaCS) from Catenulispora acidiphila and its products were identified. The enzyme mechanism was studied by isotopic labelling experiments and usage of substrate analogues with blocked reactivity, resulting in a series of derailment products. Their chemistry was studied, leading to the biomimetic synthesis of a diterpenoid analogue of a brominated sesquiterpene known from the red seaweed Laurencia microcaldia.
Abstract
A new diterpene synthase from the actinomycete Catenulispora acidiphila was identified and the structures of its products were elucidated, including the absolute configurations by an enantioselective deuteration approach. The mechanism of the cationic terpene cyclisation cascade was deeply studied through the use of isotopically labelled substrates and of substrate analogues with partially blocked reactivity, resulting in derailment products that gave further insights into the intermediates along the cascade. Their chemistry was studied, leading to the biomimetic synthesis of a diterpenoid analogue of a brominated sesquiterpene known from the red seaweed Laurencia microcladia.
https://ift.tt/2UbdgEm
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c05133
https://ift.tt/318yCXx
Hey, can someone recommend papers about the evolution of ATP synthase, and the relationship between its subunits and the subunits of other bacterial proteins such as the flagellum "motor" ? Thank you.
Hi!
It's my understanding that glycogen synthase is regulated by glycogen synthase kinase 3 (GSK3), which phosphorylates and inactivates it and phosphoproten phosphatase (PP1) which dephosphorylates is and activates it.
Yet in a diagram in my book (Lehninger) there is a line making the correlation that PKA decreases the activity of glycogen synthase. How does that work?
My guess would be that either PKA can also phosphorylate and thus deactivate glycogen synthase or that PKA maybe phosphorylates GSK3, activating that and then GSK3 phosphorylates and deactivates glycogen synthase.
Are one of my guesses correct or is something else at play here?
TIA for any answers.
Hi!
I was looking through some practice exam sets for my biochem course, and one problem kind of confused me. The problem is as such:
5-fluoro-orotate works as an inhibitor. Which enzyme in the nucleotide metabolism do you think it will ultimately inhibit?
The answer states that the enzyme it will inhibit will be thymidylate synthase. And this raises two questions to me. First of all, how do you conclude that 5-fluoro-orotate will take this "road" through the pathway, that produces dTMP?
To get there it would have to go Orotate -> OMP -> UMP -> UDP -> dUDP -> dUTP -> dUMP -> dTMP.
How am i supposed to know that it would take this "road" and not just become for example CTP, by going Orotate -> OMP -> UMP -> UTP -> CTP.
The second question is then: Why of all these steps would it only end up inhibiting the conversion to dTMP? I would think that substituting in a fluor atom would have some consequences for the enzymes affinity way earlier on. Why would the fact that an a fluor atom has been substituted in not affect for example the conversion of orotate to OMP? Or any of the other steps for that matter?
Hope someone here can help me clear this up, i appreciate any help.
Why is part of the treatment of a cystathionine synthase (homocysteine->cystathionine->cysteine) deficiency decreased intake of methionine but a methionine synthase deficiency (homocysteine->methionine) doesn't include a decrease in cysteine?
Hey folks, I recently had an exam and wanted to understand why I got a question wrong. It asked how many degrees the gamma subunit rotates to synthesize one ATP molecule. I wanted to know why the answer was 360 as opposed to 120. It’s been a head scratcher for me ever since.
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I understand why heme would do so—but can't wrap my head around why glucose (seemingly out of nowhere) can also down-regulate heme production. Does this mean that people with uncontrolled diabetes (so hyperglycemia) have impaired heme synthesis also?
Thank you.
The polyketide synthase (PKS)‐like protein TerB, consisting of inactive dehydratase, inactive C ‐methyltransferase and functional ketoreductase domains collaborates with the iterative non reducing PKS TerA to produce 6‑hydroxymellein, a key pathway intermediate during the biosynthesis of various fungal natural products. The catalytically inactive dehydratase domain of TerB appears to mediate productive interactions with TerA, demonstrating a new mode of trans‐interaction between iterative PKS components.
https://ift.tt/3rkAjvD
A new diterpene synthase from the actinomycete Catenulispora acidiphila was identified and the structures of its products were elucidated, including the absolute configurations by an enantioselective deuteration approach. The mechanism of the cationic terpene cyclisation cascade was deeply studied through the use of isotopically labelled substrates and of substrate analogs with partially blocked reactivity, resulting in derailment products that gave further insights into the intermediates along the cascade. Their chemistry was studied, leading to the biomimetic synthesis of a diterpenoid analog of a brominated sesquiterpene known from the red seaweed Laurencia microcladia.
https://ift.tt/2UbdgEm
