lecture 7 Flashcards
(23 cards)
What is the keto cousin of aspartate
oxaloacete
what is the cousin of alanine
pyruvate
what is the cousin of glutamine
glutamate
what is the cousin of glutamate
alpha keto glutamate
Which amino acids are used to transport NNH3 between tissues
Glutamine and alanine
Which amino acids are used to carry amino groups inside cells
glutamate
Which enzyme catalyzes the rxn to make glutamine
glutamine synthetase
which enzyme catalyzes the reaction to make caramel phosphate
carbamoyl phosphate synthetase
which enzyme makes glycine
glycine synthase
Which enzyme makes akg for urea cycle?
glutamate dehydrogenase
Which enzyme makes glutamine for urea cycle
glutaminase
What is the reaction catalyzed by transaminase?
aspartate +akg→← oxaloacetate +glutamate
what cofactor does transaminase use?
PLP, amino group is COVALENTLY attached to cofacto, also an electron sink, stabilizes carbanions
What is the ping part of transaminase rxn?
amino group is transferred to the cofactor, forming a pyidioximine intermediate and releasing an a-keto acid carbon skeleton
What is the pong part of the transaminase rxn?
an a-keto acid reacts with PMP to yield an amino acid
How is excess NH3 in the blood transported to the liver?
via glutamine and alanine
Where does aspartate come from in the cytosol?
aspartate transaminase makes asp from oxaloacetate, then asp is transported into the cytosol via the asp/glu transporter
What is the glucose alanine cycles
Pyruvate us made in the muscle via glycolysis
Alanine Transaminase makes akg and alanine from glu and pyruvate
Alanine transported to liver
Another alanine transaminase converts alanine to pyruvate in the liver
Gluconeogenesis makes glucose in the liver, which is the exported to the muscle
What is GDH?
glutamate dehydrogenase, oxidative deamination of glutamate
GDH is a mitochondrial enzyme that is highly expressed in the liver, it generate a-KG, NAD(P)H and free NH3
What is the urea cycle?
In the liver, carbamoyl phosphate synthase makes carbamoyl phosphate
Another c-p is added in to make citrulline
The ORNT1 antiporter exports citrulline into the cytosol
Aspartate us added to citrulline to make argininosuccinate
Arginosuccinate → fumarate → arginine
Arginine is made back into ornithine by ARGINASE, which releases urea into the cytosol
How are the urea and TCA cycles linked
fumarate can be converted to malatate and and transported into the mitochondria
ozaloacetate stuff
malate aspartate shuttle
NADH offset cost
How is the urea cycle regulated?
allosteric activation of carbamoyl phosphate synthetase by N-acetylglutamate, N acetyl glutamate are activated by arginine and glutamate (signal that nitrogen levels are high)
What happens and how do we treat ornithine transcarbamylase blockage?
conversion of ornithine to cirtulline is blocked, treat with benzoate which depleetes glycogen and glu( cells need to use NH3 to replenish)
