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28 Cards in this Set

  • Front
  • Back
Which prokaryotes can fix atmospheric nitrogen?
1. free-living soil bacteria (Azotobacter)
2. Nitrogen-fixing bacteria, symbionts of leguminous plants (Rhizobium)
How many ATP and electrons are required for nitrogen fixation?
16 ATP; 8 electrons
Nitrogen is converted to ammonia by the ?.
Nitrogenase complex.
In nitrogen fixation, electrons are transferred from ? to ? via ? and ?.
pyruvate; dinitrogenase; ferredoxin (or flavodoxin); denitrogenase reducatase
Ammonia is incorporated into biomecules through ? and ?.
Glutamate and Glutamine
What is the main regulatory enzyme in nitrogen metabolism?
Glutamine synthetase
What serves as allosteric inhibitors of glutamine synthesis?
alanine, glycine, and 6 end products of glutamine metabolism
The alternative pathway of glutamate synthesis (minor) is catalyzed by ?
glutamate dehydrogenase
Glutamine synthetase is also regulated by what other mechanism?
covalent modifications
Adenylation of ? inhibits enzymatic activity of glutamine synthetase.
Both adenylation and deadenylation of glutamine synthetase are promoted by which enzyme?
adenylyltransferase (AT)
The activity of P(II) is regulated by ?.
uridylyltransferase (UT)
The adenylyltransferase complex with uridylylated P(II) stimulates ?.
deadenylation of glutamine synthetase making it active
Does uridylylated P (II) increase or decrease transcription of the gene encoding glutamine synthetase?
How do animals maintain high levels of glutamate?
By transamination of α-keotglutarate during amino acid metabolism
What is the prosthetic group of aminotransferases/transaminases?
Pyridoxal phosphate (PLP)
Transfer of one carbon groups occurs with either ? or ? as cofactor.
tetrahydrofolate; S-adenosyl-Methionine
What are glutamine amidotransferases?
Enzymes in biosynthetic reactions that use glutamine as a major physiological source of amino group.
What are the two domains in glutamine amidotransferases?
The glutamine binding domain (conserved w/ Cys in the active center) and the NH3 acceptor domain (varies).
What is the covalent intermediate hydrolyzed to?
Glutamate and the free enzyme
From where are the carbon skeleon precursors of amino acids derived?
glycolysis, citric acid cycle, pentose phosphate pathway
Describe how proline can also be synthesized from ariginine obtained from dietary or tissue protein.
Arginase, the urea cycle enzyme, converts arginine to ornithine and urea. The ornithine is then converted to glutamate-gammma-semialdehyde by ornithine delta-aminotransferase.
What enzyme is responsible for removing a carbon atom from serine to generate glycine?
Serine hydroxymethyltransferase
What cofactor is required for serine hydroxymethyltransferase?
tetrahydrofolate, the overall reaction requires PLP also.
Glycine synthase is required to make glycine from ? and ?.
CO2 and NH4
Where in vertebrates can glycine be made?
In the liver via glycine synthase (from CO2 and NH4)
How is cysteine generated?
Methionine furnishes the sulfur atom and serine supplies the carbon skeleton.
How is homocystein formed?
From methionine via S-adenosylmethionine and S-adenosylhomocysteine.