Chapter 31 - Amino Acid Synthesis Flashcards
diazotrophic bacteria
organisms that can convert nitrogen gas to biochemically more useful, NH3
The Haber process
allows for industrial fixation of nitrogen
_________ and ________ are forms of nitrogen that are available to plants
ammonium and nitrates
Nitrates are reduced to ________.
ammonium
the nitrogenase complex
-consists of two proteins, reductase and nitrogenase
reductase
provides e- with high reducing power
nitrogenase
uses ,e- to reduce N2 to NH3
The ammonia produced in plants is…
directly used by the plants
The ammonia produced by nitrogen-fixing microorganisms in the soil is…
converted to nitrite, then to nitrate by other bacteria
-nitrate (NO3-) is taken up my plants and reduced to NH3
Step 2: ___________ and _________ provide entry points to assimilation of ammonia to biomolecules
glutamate and glutamine
glutamate dehydrogenase
NH4+ and aKG to glutamate
glutamine synthetase
glutamate + NH4+ to glutamine
glutamate synthase (last rxn)
aKG + glutamine to glutamate
Step 3 of Assimilation of Nitrogen
glutamate and glutamine donate an amino group in other biosynthetic pathways
The carbon skeletons for aa synthesis are provided by intermediates of…
the glycolytic pathway, citric acid cycle, and pentose phosphate pathway
Glutamine synthetase is present in …
all organisms
Gln synthetase is regulated by:
allosteric effectors (all 6 end product) and covalent codification (adenylation)
adenylation
addition of AMP (occurs on a Try residue)
structure of glutamine synthetase
12 identical subunits
transamination rnx enzyme and coenzyme
- aminotransferase
- pyridoxal phosphate (vit B6)
1-carbon transfer rxn enzyme cofactors (1C carriers and 1C donors)
- S-adenosyl methionine (SAM) donates methyl group
- tetrahydrofolate
glutamine amidotransferase
transfer of an amino or amide group from glutamine
1C transfer using SAM
methyl group transfers to a nitrogen or oxygen atom
1C transfer rxns using tetrahydrofolate (TH4) catalyzed by?
dihydrofolate reductase
essential amino acids
valine, leucine, isoleucine, tryoptophan, phenylalanine, histidine, methionine, threonine, lysine
6 metabolic precursors
- aKG
- pyruvate
- 3-phosphoglycerate
- oxaloacetate
- phosphoenol pyruvate and erythrose 4-P
- ribose 5-P
Which amino acid(s) can be synthesized by the metabolic precursor a-KG
glutamate, glutamine, proline, arginine
Which amino acid(s) can be synthesized by the metabolic precursor pyruvate
alanine, valine, leucine, isoleucine
Which amino acid(s) can be synthesized by the metabolic precursor 3-phosphoglycerate
serine, glycine, cysteine
Which amino acid(s) can be synthesized by the metabolic precursor phosphoenol pyruvate and erythrose 4-P
tryptophan, phenylalanine, tyrosine
Which amino acid(s) can be synthesized by the metabolic precursor ribose 5-P
histidine
conditionally essential amino acids
arginine, cysteine, glutamine, glycine, proline, tyrosine
nonessential amino acids
alanine, asparagine, aspartate, glutamate, serine
Which amino acid(s) can be synthesized by the metabolic precursor oxaloacetate
aspartate, asparagine, methionine, threonine, lysine
4 types of feedback inhibition
- product inhibition
- sequential
- concerted
- enzyme multiplicity
regulation of synthesis of amino acids from oxaloacetate by feedback inhibition
- sequential
- enzyme multiplicity
- concerted inhibition
