module 12- amino acid synthesis Flashcards
what is the endpoint of nitrogen fixation
ammonium
glutamate dehydrogenase
a-ketoglutarate -> glutamate
glutamine synthetase
glutamate -> glutamine
glutamate synthase
a-ketoglutarate -> 2 glutamate
what is the regulatory enzyme of nitrogen metabolism
glutamine synthetase
T or F: glutamine synthetase is present in all organisms
T
ubiquitous enzyme
present in all organisms
how is glutamine synthetase regulated (2)
covalent modification & allosterically
how many allosteric inhibitors? how many come from glutamine and how many from amino acids
8 total, 6 from glutamine & 2 from amino acids
concerted inhibition
effects are more than additive
allosteric inhibitors are ( ) inhibition
concerted
covalent modification of glutamine synthetase
adenylylation
adenylylation
linking AM to tryosine
glutamine synthetase is a ( ) structure
quaternary & has multiple subunits which each have an active site
consequence of adenylylation
insensitive to allosteric inhibitors, need combination of covalent & allosteric to control activity
SAM
adds methyl groups
why is SAM used over methione?
methionine is not very reactive
methyl groups are almost always transferred to a ( ) or ( ) atom
nitrogen or oxygen
N-methyltransferase
SAM transfers nitrogen to norepinephrine
what is tetrahydrofolate derived from
vitamin B9 (folate)
what does N5 & N10 indicate?
indicate specific atoms in tetrahydrofolate to which carbons are attached
source of one-carbon units
serine or formate, oxygen, nitrogen
T or F: tetrahydrofolate is a carrier of very diverse types of one-carbon units
aspargaine synthetase
aspartate -> asparagine
T or F: both glutamine & glutamate act as amino group donors at different steps of the synthetic pathway for histidine in plants
T
what 3 metabolic pathways supply the intermediates that amino acids are synthesized from?
glycolysis, pentose phosphate, CAC
conditionally essential amino acids
essential only during specific points
what are the 5 non-essential amino acids
alanine, asparagine, aspartate, glutamate & serine
what amino acids can be derived from oxaloacetate
aspartate, asparagine, methionine, lysine, & threonine
what amino acids can be derived from pyruvate
alanine, valine, leucine & isoleucine
what is used as an amino group donor in lysine pathway
glutamate
product inhibition
end product acts as allosteric inhibitor of 1st step
- prevents unnecessary production of F when levels are sufficient
sequential inhibition
branched into 2 end points, F & G inhibit 1st committed step
F & G inhibit the conversion of C to D and E, and C acts back on A to B
concerted inhibition
F & G inhibit A to B
enzyme multiplicity
2 isoenzymes are inhibited by F or G
allows fine tuning
what 2 molecules provide entry points for the assimilation of ammonium into biomolecules
glutamine & glutamate
what process does glutamate donates its amino groups for the synthesis of other amino acids?
transamination
what 2 molecules provide 1 carbon units for the synthesis of biomolecules
tetrahydrofolate derivatives & SAM
oxaloacetate is a direct precursor for which animo acid?
aspartate
