Amino Acids (Lecture 25)

Question 1

what is the enzyme reaction for the first step of deamination and where does this occur?

Answer 1

the glutaminase reaction is the first step of deamination, which occurs in the liver.

glutaminase will convert glutamine into glutamate and it will also release an NH4(amino group), which is detoxified via the urea cycle.

Question 2

what is the enzyme reaction for the second step of deamination and where does this occur?

Answer 2

glutamate dehydrogenase reaction occurs in the mitochondrial matrix of the liver, kidney and nervous tissue.

glutamate dehydrogenase uses NAD(P)+ as a co-enzyme.

this reaction will yield alpha KG (CAC) and a nitrogen (urea cycle)

Question 3

what are the allosteric activators/inhibitors of GDH?

Answer 3

when energy state is low, [ADP/NADP+] is high= activator

high energy state, [GTP/NADPH] high= inhibitor

Question 4

what is the driving for the glutamate DH?

Answer 4

there is a shortage of alpha KG (CAC intermediate) which will drive the reaction forward (oxidative deamination)

Question 5

what is the transamination pair of glutamate?

Answer 5

alpha KG

Question 6

what is the transamination pair of aspartate?

Answer 6

oxaloacetate

Question 7

what is transamination (general meaning)?

Answer 7

amino acid is transformed into a keto acid

NH3 group to keto group =O

Question 8

all transaminases have ____ as a coenzyme

Answer 8

PLP

Question 9

what is funneling (and the preferred pair)

Answer 9

most amino acids prefer alpha KG/ Glutamate pair for funneling.

funneling is used in transamination reactions to convert a pair of aa/ketoacid into a ketoacid/aa.

this is a transamination reaction because the an amine group is added to one keto acid, while an amino group is cleaved from the other aa

Question 10

how is PLP (pyridoxal phosphate) syntehsized?

Answer 10

synthesized via transamination reaction, thus it will eventually act as a carrier for amino groups.

Vitamin B6 is the molecule used to synthesize PLP.

Question 11

which molecule acts as the NH3 carrier in the PLP reaction?

Answer 11

PMP will acquire an amino group as for PLP will be synthesized via Vitamin B6 (OH-> =O) and then PLP will undergo a transaminase reaction to gain an amine group and form PMP

Question 12

what is the ping pong mechanism for transamination? (5)

Answer 12

1. enzyme binds to PLP to make a Schiff base
2. the aa1 will form an external Schiff base with PLP by cleaving off the enzyme
3. hydrolysis reaction releases a keto-acid1 (PMP)
4. keto-acid2 binds to the PMP, in which a Schiff base is formed
5. regeneration of PLP-enzyme, which releases amino acid2

Question 13

most transaminase reaction prefer ____ as the keto acid 2

Answer 13

alpha KG

Question 14

what is type II tyrosinemia?

Answer 14

defficiiency in tyrosine aminotransferase (transaminase deficiency)

it cannot convert tyrosine into the desired compound, which impacts the synthesis of many hormones

Question 15

what is the Cahill cycle?

Answer 15

glucose (tissue)
pyruvate (tissue)
alanine (tissue)
alanine(blood)
alanine(liver)
pyruvate (liver)
glucose (liver)
glucose (blood)
glucose (tissue)

Question 16

Cahill cycle using ALT1/2

Answer 16

in the muscle, when protein are used as a osurce of energy, amino acids will be broken down, thus producing NH4 (toxic)

the NH4 will partake in a transamination reaction to form glutamate from alpha KG

now glutamate can serve in the alanine transaminase reaction, where pyruvate is converted into alanine via ALT 2 (muscle)

alanine is then transported into he liver and will undergo the opposite reaction

in the liver alpha KG and aklanien will undergo a transaminase reaction to form glutamate and pyruvate via ALT1 (liver)

the pyruvate will then synthesize glucose for glycolysis

Question 17

where is ALT-1 found and which keto acid does it use?

Answer 17

liver

alpha KG

Question 18

where is ALT-2 found and which keto acid does it use?

Answer 18

muscle

pyruvate