Transcript Metabolism of amino acids - exercise - Vladimíra Kvasnicová

Metabolism of amino acids
- exercise -
Vladimíra Kvasnicová
Choose essential amino acids
a) Asp, Glu
b) Val, Leu, Ile
c) Ala, Ser, Gly
d) Phe, Trp
Choose essential amino acids
a) Asp, Glu
b) Val, Leu, Ile
c) Ala, Ser, Gly
d) Phe, Trp
Essential amino acids
„10“
1) branched chain:
Val, Leu, Ile
2) basic:
His, Arg, Lys
3) aromatic:
Phe
(→ Tyr),
4) sulfur-containing:
Met
(→ Cys)
5) other:
Thr
Trp
Choose amino acids from which the
other amino acid can be synthesized in
a human body
a) valine → leucine
b) aspartate → asparagine
c) phenylalanine → tyrosine
d) methionine + serine → cysteine
Choose amino acids from which the
other amino acid can be synthesized in
a human body
a) valine → leucine
leucine is the essential AA
b) aspartate → asparagine
c) phenylalanine → tyrosine
d) methionine + serine → cysteine
Synthesis of
ASPARAGINE
needs glutamine as
–NH2 group donor
(it is not ammonia as
in the Gln synthesis)
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Synthesis of Tyr from Phe
The figure is from http://web.indstate.edu/thcme/mwking/amino-acid-metabolism.html (Jan 2007)
Synthesis of Cys from Met and Ser
The figure is from http://web.indstate.edu/thcme/mwking/amino-acid-metabolism.html (Jan 2007)
The amino acids can be formed from the
citrate cycle intermediates
in a human body
a) -ketoglutarate → glutamate
b) succinyl-CoA → isoleucine
c) oxaloacetate → aspartate
d) malate → threonine
The amino acids can be formed from
the citrate cycle intermediates
in a human body
a) -ketoglutarate → glutamate
b) succinyl-CoA → isoleucine
Ile is the essential AA
c) oxaloacetate → aspartate
d) malate → threonine
Thr is the essential AA
Amphibolic
character
of citrate cycle
The figure is from
http://www.tcd.ie/Biochemistry/IUBMB-Nicholson/gif/13.html (Dec 2006)
The compound(s) can be synthesized
from the amino acid
a) tyrosine → serotonin
b) serine → ethanolamine
c) tryptophan → catecholamines
d) cysteine → taurine
The compound(s) can be synthesized
from the amino acid
a) tyrosine → serotonin
Tyr → catecholamines
b) serine → ethanolamine
formed by decarboxylation
c) tryptophan → catecholamines
d) cysteine → taurine
Trp → serotonin
taurin is used in conjugation reactions in the liver
– it is bound to hydrophobic substances to increase their solubility
(e.g. conjugation of bile acids)
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
If the amino acid is metabolised the
substance is formed:
a) methionine gives homocysteine
b) serine gives glycine and folic acid
derivative: methylene tetrahydrofolate
c) glutamine releases ammonia
d) some amino acides can be degraded to
acetoacetate
If the amino acid is metabolised the
substance is formed:
a) methionine gives homocysteine
b) serine gives glycine and folic acid
derivative: methylene tetrahydrofolate
c) glutamine releases ammonia
d) some amino acides can be degraded to
acetoacetate = one of ketone bodies
Regeneration of
Met
B12
(vitamins: folate+B12)
The figure is from http://web.indstate.edu/thcme/mwking/amino-acid-metabolism.html (Jan 2007)
glycolysis
Synthesis of serine and glycine
The figure is from http://www.biocarta.com/pathfiles/GlycinePathway.asp (Jan 2007)
Choose products of the transamination
reactions
a) alanine → pyruvate
b) glutamate → 2-oxoglutarate
c) aspartate → oxaloacetate
d) phenylalanine → tyrosine
Choose products of the transamination
reactions
a) alanine → pyruvate
b) glutamate → 2-oxoglutarate
c) aspartate → oxaloacetate
d) phenylalanine → tyrosine
it is not transamination
Transamination reaction
! REVERSIBLE !
enzymes: amino transferases
coenzyme: pyridoxal phosphate (vit. B6 derivative)
The figure is from http://web.indstate.edu/thcme/mwking/nitrogen-metabolism.html (Jan 2007)
Amino transferases important in medicine
(„transaminases“)
alanine aminotransferase
(ALT = GPT)
aspartate aminotransferase
(AST = GOT)
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Amino nitrogen released from carbon
sceletons of AAs can be transported in
blood as
a) NH4+
b) alanine
c) glutamine
d) urea
Amino nitrogen released from carbon
sceletons of AAs can be transported in
blood as
a) NH4+ physiologically up to 35 µmol/l (NH3 + H +
b) alanine
formed by transamination from pyruvate
c) glutamine
d) urea
NH4+)
the most important transport form of –NH2
it is the end product of degradation of amino nitrogen
(liver → kidneys → urine)
Transport of
amino nitrogen
from degraded
muscle proteins
products
excreted
with urine
The figure was adopted from Devlin, T. M. (editor): Textbook
of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss,
Inc., New York, 1997. ISBN 0-471-15451-2
Glucose-alanine cycle
alanine transfers
both the carbon
sceleton for
gluconeogenesis
and –NH2 group
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
GLUTAMINE
= the most important
transport form af amino
nitrogen in blood
glutamine synthetase
it transfers two amino
groups released by
degradation of AAs
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Choose glucogenic amino acids
a) alanine
b) lysine
c) leucine
d) glutamine
Choose glucogenic amino acids
a) alanine
b) lysine
c) leucine
d) glutamine
7 degradation products of AAs
1. pyruvate  Gly, Ala, Ser, Thr, Cys, Trp
2. oxaloacetate  Asp, Asn
3. -ketoglutarate  Glu, Gln, Pro, Arg, His
4. succinyl-CoA  Val, Ile, Met, Thr
5. fumarate  Phe, Tyr
6. acetyl-CoA  Ile
glucogenic AAs
ketogenic AAs
7. acetoacetyl-CoA  Lys, Leu, Phe, Tyr, Trp
Glutamate dehydrogenase (GMD)
a) catalyzes conversion of Glu to oxaloacetate
b) is found in mitochondria of hepatocytes
c) produces ammonia
d) needs pyridoxal phosphate as a coenzyme
Glutamate dehydrogenase (GMD)
a) catalyzes conversion of Glu to oxaloacetate
b) is found in mitochondria of hepatocytes
c) produces ammonia
d) needs pyridoxal phosphate as a coenzyme
GLUTAMATE DEHYDROGENASE
removes amino group from carbon sceleton of Glu in the liver
1. –NH2 from AAs was transfered by transamination → Glu
2. free ammonia is released by oxidative deamination of Glu
The figure is from http://web.indstate.edu/thcme/mwking/nitrogen-metabolism.html (Jan 2007)
Choose correct statement(s) about
metabolism of amino acids
a) alanine aminotransferase (ALT) transforms
pyruvate to alanine
b) aspartate aminotransferase (AST) transforms
aspartate to -ketoglutarate
c) glutamine synthetase transforms glutamate to
glutamine
d) glutaminase catylyzes conversion of glutamine
to ammonia and -ketoglutarate
Choose correct statement(s) about
metabolism of amino acids
a) alanine aminotransferase (ALT) transforms
pyruvate to alanine
b) aspartate aminotransferase (AST)
transforms aspartate to -ketoglutarate
c) glutamine synthetase transforms glutamate
to glutamine
d) glutaminase catylyzes conversion of
glutamine to ammonia and -ketoglutarate
Amino transferases important in medicine
(„transaminases“)
alanine aminotransferase
(ALT = GPT)
aspartate aminotransferase
(AST = GOT)
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Glutamine is principal
transport form of amino nitrogen
The figure is from http://www.sbuniv.edu/~ggray/CHE3364/b1c25out.html (Dec 2006)
The amino acids can enter the citrate
cycle as the molecules
a) alanine → → acetyl-CoA
b) aspartate → oxaloacetate
c) valine → → succinyl-CoA
d) glutamine → → -ketoglutarate
The amino acids can enter the citrate
cycle as the molecules
a) alanine → → acetyl-CoA
b) aspartate → oxaloacetate
c) valine → → succinyl-CoA
d) glutamine → → -ketoglutarate
The entrance of amino acids into the citrate cycle
The figure is from http://www.biocarta.com/pathfiles/glucogenicPathway.asp (Jan 2007)
Ornithine cycle
a) proceeds only in the liver
b) produces uric acid
c) includes arginine as an intermediate
d) produces energy in a form of ATP
Ornithine cycle
a) proceeds only in the liver
b) produces uric acid
c) includes arginine as an intermediate
d) produces energy in a form of ATP
Detoxication of ammonia in the liver
The figure is from http://www.biocarta.com/pathfiles/ureacyclePathway.asp (Jan 2007)
Interconnection of the urea cycle with the
citrate cycle
The figure is from http://courses.cm.utexas.edu/archive/Spring2002/CH339K/Robertus/overheads-3/ch18_TCA-Urea_link.jpg
(Jan 2007)
In the urea synthesis
a) ammonia reacts with ornithine → citrulline
b) carbamoyl phosphate synthetase I (=
mitochondrial) regulates the cycle
c) aspartate is used as a –NH2 group donor
d) urea is formed – it can be used as an energy
substrate for extrahepatic tissues
In the urea synthesis
a) ammonia reacts with ornithine → citrulline
b) carbamoyl phosphate synthetase I (=
mitochondrial) regulates the cycle
c) aspartate is used as a –NH2 group donor
d) urea is formed – it can be used as an energy
substrate for extrahepatic tissues
Regulation of urea cycle
allosteric regulation + enzyme induction by protein rich diet or
by metabolic changes during starvation
regulatory enzyme
activation
carbamoyl phosphate
synthetase I
(= mitochondrial)
 N-acetylglutamate
N-acetylglutamate
synthetase
 arginine
Urea synthesis is inhibited by acidosis
– HCO3- is saved
inhibition