lecture 7

Question 1

What is the keto cousin of aspartate

Answer 1

oxaloacete

Question 2

what is the cousin of alanine

Answer 2

pyruvate

Question 3

what is the cousin of glutamine

Answer 3

glutamate

Question 4

what is the cousin of glutamate

Answer 4

alpha keto glutamate

Question 5

Which amino acids are used to transport NNH3 between tissues

Answer 5

Glutamine and alanine

Question 6

Which amino acids are used to carry amino groups inside cells

Answer 6

glutamate

Question 7

Which enzyme catalyzes the rxn to make glutamine

Answer 7

glutamine synthetase

Question 8

which enzyme catalyzes the reaction to make caramel phosphate

Answer 8

carbamoyl phosphate synthetase

Question 9

which enzyme makes glycine

Answer 9

glycine synthase

Question 10

Which enzyme makes akg for urea cycle?

Answer 10

glutamate dehydrogenase

Question 11

Which enzyme makes glutamine for urea cycle

Answer 11

glutaminase

Question 12

What is the reaction catalyzed by transaminase?

Answer 12

aspartate +akg→← oxaloacetate +glutamate

Question 13

what cofactor does transaminase use?

Answer 13

PLP, amino group is COVALENTLY attached to cofacto, also an electron sink, stabilizes carbanions

Question 14

What is the ping part of transaminase rxn?

Answer 14

amino group is transferred to the cofactor, forming a pyidioximine intermediate and releasing an a-keto acid carbon skeleton

Question 15

What is the pong part of the transaminase rxn?

Answer 15

an a-keto acid reacts with PMP to yield an amino acid

Question 16

How is excess NH3 in the blood transported to the liver?

Answer 16

via glutamine and alanine

Question 17

Where does aspartate come from in the cytosol?

Answer 17

aspartate transaminase makes asp from oxaloacetate, then asp is transported into the cytosol via the asp/glu transporter

Question 18

What is the glucose alanine cycles

Answer 18

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

Question 19

What is GDH?

Answer 19

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

Question 20

What is the urea cycle?

Answer 20

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

Question 21

How are the urea and TCA cycles linked

Answer 21

fumarate can be converted to malatate and and transported into the mitochondria
ozaloacetate stuff
malate aspartate shuttle
NADH offset cost

Question 22

How is the urea cycle regulated?

Answer 22

allosteric activation of carbamoyl phosphate synthetase by N-acetylglutamate, N acetyl glutamate are activated by arginine and glutamate (signal that nitrogen levels are high)

Question 23

What happens and how do we treat ornithine transcarbamylase blockage?

Answer 23

conversion of ornithine to cirtulline is blocked, treat with benzoate which depleetes glycogen and glu( cells need to use NH3 to replenish)