Final Amino acid Bio synthesis Flashcards
What are the three efficient solutions to important biochemical problems?
- obtain nitrogen in a usable form
- exercise strict stereochemical control
- restrict AA production only when supplies are very limited
Nitrogen in biological systems is ultimately derived from atmospheric N2 through a reductive process called?
Nitrogen Fixation
Fixation requires cleavage of the triple bond found in N2 and it is super strong. How is it possible to turn it into NH3, even though it produces unstable intermediates
it requires a specialized catalyst
What can be found in root nodules?
Symbiotic nitrogen-fixing bacteria that can carry our nitrogen fixation
n biological settings, the reduction of N2 to NH3 is carried out by an enzyme assembly called ?
nitrogenase complex
Still, diazotrophic organisms account for only about 60% of N2 fixation on Earth. The remainder occurs through…….. processes or through an industrial reaction called the …… process:
- photo electric process
- baer bosch process
What is the nitrogenase complex composed of?
reductase- provides high reducing potential electrons
nitrogenase- use electrons to reduce N2 to NH3
for nitrogen fixation ATP hydrolysis purpose is to ?
used to lower the kinetic activation barriers to the pathway!
what is the term used to describe organisms that are capable of nitrogen fixation
diazotrophic
What is the fate of the ammonium ions after fixation?
This ammonium ion is assimilated into glutamate and glutamine, - play critical roles in the biosynthesis of other nitrogen-containing compounds.
Amino Acid are Made from
Intermediates of the Citric Acid Cycle and Other Major Pathways
TCA we get what metabolites
OAA - asperate and a-Ketogluterate- glutamate
In glycolysis we get what metabolites
Pyruvate and 3- Phosphoglycerate
glycolysis and pentose phosphate ptwy we get what metabolites
Phosphoenolpyruvate + erythrose 4- phosphate
Pentose ptwy we get what metabolites
ribose 5 - phosphate
Which amino acids result from the transamination of pyruvate and
oxaloacetate
Alanine and asperate
Most microorganisms can synthesize the entire basic set of 20 amino acids. This is not the case for humans, and 9 of the twenty must be taken in adequate dietary supply. These are denoted the essential amino acids:
Histidine
Isoleucine
leucine
lysine
methionine
phenylalanine
threonine
tryptophan
valine
The Biosynthetic Pathways for Essential Amino Acids Are Generally More Involved Than Those of the Nonessential Ones
true or false
true - require more steps
when there is an abundant of a- ketoacid’s what is formed through transamination?
Aspartate, Alanine, and Glutamate
α-ketoglutarate can be converted into glutamate using free ammonium ion and the enzyme glutamate dehydrogenase.
Once formed, glutamate can serve as an amino group donor for the transamination of?
oxaloacetate and pyruvate
What is the most abundant amino acid in cells
glutamate
how are glutamine and asparagine synthesized?
- The formation of asparagine from aspartate (catalyzed by asparagine synthetase) is chemically analogous to the formation of glutamine from glutamate
- both require ATP hydrolysis
How does asperate get to asparagine
catalyzed by asparagine synthetases but uses an acyl-adenylate intermediate
Glutamate can serve as an amino group donor for ….
transamination of oxaloacetate and pyruvate
The formation of asparagine from aspartate require what intermediate ?
acyl-adenylate intermediate
In mammals, the source of ammonium is actually ……., which is hydrolyzed in the enzymatic active site.
glutamine
Glutamate is the precursor for
Glutamine, Proline, and Arginine
transamination of α-ketoglutarate can give us the formation of ?
glutamate
what is Glutamic γ-semialdehyde formed from?
When the Glutamate γ-phosphate group of reacts with ATP it forms an acyl-phosphate intermediate, then reduced NADPH.
What are the two metabolic fates of Glutamic γ-semialdehyde
- An enzymatic dehydration of Glutamic γ-semialdehyde to yield delta 1-pyroline 5-carboxylate, which can be reduced by NADPH to yield proline.
- transamination by glutamate to produce ornithine then through urea cycle to produce arginine
3-Phosphoglycerate is the Precursor for?
Serine, Cysteine, and Glycine
3-Phosphoglycerate is an intermediate in what process?
glycolysis
The formation of serine is required to generate what ?
cysteine and glycine
what is the first step in serine production?
- 3-phosphoglycerate is NAD+- oxidation to produce 3-phosphohydroxypruvate
- transamination to yield 3-phosphoserine
- hydrolysis to serine
what must serine interact with in order to get the formation of cysteine and glycine?
new activated group carriers of one-carbon groups
tetrahydrofolate and S-Adenosylmethionine, what is their purpose
used as new activated group carriers of one-carbon groups and interact with serine to produce cysteine and glycine
The regulation of metabolic flux through pathways of amino acid biosynthesis is regulated both by
enzyme levels
activity level
Let’s consider the synthesis of serine. The committed step in this pathway is?
oxidation of 3-phosphoglycerate catalyzed by 3-phosphoglycerate dehydrogenase
The E. coli enzyme is a tetramer comprising catalytic and regulatory regions. The binding of serine to a regulatory site causing ?
reduced vmax of enzyme
enzyme bound to four serines is essentially inactive
if serine is abundant in the cell, the enzymatic activity is?
blocked and 3-phosphoglycerate can be used for other processes.
When considering amino acid biosynthesis, we have encountered several pathways where a common intermediate precursor is ultimately converted into two different products. The regulation of these branched pathways is more complicated because two products must be accounted for. What are the four main strategies for regulation?
- Feedback inhibition and activation
- Enzyme multiplicity
- Cumulative feedback inhibition
- Reversible covalent modification
Sometimes, two pathways are parallel with common intermediates, what helps balance the flux of production?
two pathways with a common intermediate may each be inhibited by their product and activated by the product of the other
an example of two pathways with a common intermediates being inhibited by their product and activated by the product of the other.
When threonine is converted into α- ketobutyrate in the committed step, it leads to the synthesis of isoleucine.
The enzyme threonine deaminase is inhibited when the levels of Isoleucine are elevated but activated by valine
What is the regulation of enzyme multiplicity ?
In this strategy, a committed step can be catalyzed by two or more enzymes, each with a distinct set of regulatory properties
What is an example of enzyme multiplicity
An example of this is the phosphorylation of aspartate in E. coli. committed step of the biosynthesis of methionine and threonine
one enzyme is not subject to feedback inhibition,
another is inhibited by threonine,
the third is inhibited by lysine
what is Cumulative feedback inhibition
A common metabolic step can be partly inhibited by each of the final products, acting independently.
The activity of glutamine synthetase in E. coli is regulated . The amide group of glutamine is an important nitrogen donor in the biosynthesis of a variety of molecules, including tryptophan, histidine, and carbamoyl phosphate. Each of these endpoints contributes partially to feedback inhibition of the synthetase. this is an example of ?
Cumulative feedback inhibition
what is Reversible covalent modification?
a modified form of an enzyme is either more or less active than the unmodified form.
glutamine synthetase is regulated by the attachment of an AMP unit to the hydroxyl group of a specific tyrosine in each subunit. This makes it a less active enzyme. This is an example of what type of regulation?
Reversible covalent modification
Amino acids can only be precursors for proteins, True of false?
false-many different biomolecules that arise from amino acid precursors.
