Key Reactions In Amino Acid Biosynthesis

Question 1

Common features in amino acid biosynthesis

Answer 1

Transamination

One-carbon transfers

Question 2

Transamination

Answer 2

The transfer of amino groups from one molecule to another; an important process in the anabolism and catabolism of amino acids

Question 3

Citric acid cycle

Answer 3

Closely associated with amino acid metabolism
(a-ketoglutarate, pyruvate, acetyl-CoA)
Amphibolic (anabolic and catabolic)

Question 4

Glutamate dehydrogenase and glutamine sythetase similarity and difference

Answer 4

Both responsible for most of NH4 assimilation
GS has lower Km than GDH
(Low nitrogen concentration - GS reaction favored)

Question 5

Pyridoxal phostohate

Answer 5

Active form of VitB6
Catalyses transamination and decarboxylation and racemazation reactions
All reactions are reversible

Question 6

PyrP mechanism

Answer 6

PyrP forms imine with a-amino group of amino acid
Rearrangement gives isometric imine
Hydrolysis give a-ketoacid and pyradoxamine
Pyradoxamine forms schiff base with acceptor substrate
Rearrangement and hydrolysis result in new amino acid and PyrP regenerated

Question 7

Imine

Answer 7

Schiffs base

Question 8

Racemazation reaction

Answer 8

Conversion of amino acids from the L-form to D-form

Creates quinonoid intermediate

Question 9

Transfer of one carbon unit

Answer 9

One-carbon transfer
Enzyme for serine (serine hydroxymethylase)
The one-carbon acceptor is tetrahydrofolate (folic acid derivative)

Question 10

Reduction of folic acid

Answer 10

Tetrahydrofolic acid (THF)

Question 11

THF 3 parts

Answer 11

Pteridine ring
P-aminobenzoic acid
Glutamic acid

Question 12

Serine one carbon transfer equation

Answer 12

Serine + tetrahydrofolate —> glycine + methylenetetrahydrofolate + H2O

Question 13

Other one carbon carriers

Answer 13

S-adenosylmethionine (SAM)
Cobalamine (Vit B12)
Biotin (Vit B7 or Vit BH)

Question 14

SAM

Answer 14

Results in S-adenohomocystein
Which is Hydrolysed into homocysteine
Homocysteine and serine result in cysteine
Only pathway for cysteine production in animals

Question 15

Cobaline

Answer 15

Vit B12
Generates tetrahydrofolate and methionine
Helps produce nucleic acids and red blood cells
Deficiency results in anaemia

Question 16

Biotin

Answer 16

Vit B7
Carbon dioxide transfer with carboxylase enzymes
Covalently attaches to these enzymes through lysine residues
Branched chain amino acid catabolism

Question 17

Biotinylation requires

Answer 17

Requires ATP and the enzyme halocarboxylase synthetase