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Yulia Suciati
METABOLISM
OF AMINO ACIDS
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OVERVIEW OF AMINO ACID METABOLISM
ENVIRONMENT ORGANISM
Ingested
protein
Bio-
synthesisProtein
AMINOACIDS
NitrogenCr!on
s"e#etons
$re
Degradation
(required)
12 3
a
b
PurinesPyrimidinesPorphyrins
c c
Used for
energypyrua!e"#$e!o%&u!ara!esucciny'oA(umara!eo)a&oace!a!e
ace!oace!a!eace!y& 'oA
*glucogenic)(ketogenic)
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NITROGEN +A,AN'E
Ni!ro%en ba&ance - ni!ro%en in%es!ed # ni!ro%en e)cre!ed
*primari&y as pro!ein. *primari&y as urea.
Ni!ro%en ba&ance - / *nitrogen equilibrium)
pro!ein syn!hesis - pro!ein de%rada!ion
Posi!ie ni!ro%en ba&ance
pro!ein syn!hesis 0 pro!ein de%rada!ion
Ne%a!ie ni!ro%en ba&ance
pro!ein syn!hesis pro!ein de%rada!ion
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N balance = NN balance = Ninin
- N- Noutout
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Positive Nitrogen BalancePositive Nitro
gen Balance
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Negative Nitrogen BalanceNegative Nitrogen Balance
1. Stress
2. Decreased Intake
3. Lack of an essential AA
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Metabolic Pool of Amino AcidsMetabolic Pool of Amino Acids
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A%ino A&id Re'(ire%ents o) *(%ns
--------------------------------------------------------------------N(trition##y Essenti# N(trition##y Nonessenti#
--------------------------------------------------------------------Ar%inine
a A&anine
is!idine Aspara%ine
Iso&eucine Aspar!a!e
,eucine 'ys!eine
,ysine G&u!ama!e
Me!hionine G&u!amine
Pheny&a&anine G&ycine
Threonine Pro&ine
Tryp!ophan Serine
Va&ine Tyrosine
---------------------------------------------------------------------a Nu!ri!iona&&y semiessen!ia&45 Syn!hesi6ed a! ra!es
inade7ua!e !o suppor! %ro8!h o( chi&dren4
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Glucose-alanine cycle
Alais the carrier of ammonia and of the carbon
skeleton of yru!ate from muscle to li!er.
"he ammonia is e#creted and the yru!ate is
used to roduce $lucose% &hich is returned to
the muscle.
Alaninelays a secial role in
transortin$ amino $rous to li!er.
Accordin% !o 94 ,4 Ne&son: M4 M4 'o) ;,ENINGER4 PRIN'IP,ES O< +IO'EMISTR=
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"he fate of the amino $rou durin$ amino acid catabolism
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'linicaly imortant transaminases
ALT
Alanine--keto$lutarate transferase ALT(also called glutamate-pyru!ate transaminase ) GPT*
Asartate--keto$lutarate transferase AST
(also called glutamate-o#alacetate transferase ) GOT*
Imortant in the dia$nosis of heart and li!er dama$e caused by heart
attack% dru$ to#icity% or infection.
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>REA '=',E
mi!ochondriacy!oso&
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Metabolism of some
selected amino acids
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+istidine ,etabolism
+istamine ormation
N
N
HCH2CHCO2
-
NH3
+
N
N
HCH2CH2NH2
+istidine +istamine
+istidine
decarbo#ylase
CO2
+istamine
Synthesi/ed in and released by mast cells,ediator of aller$ic resonse !asodilation%
bronchoconstriction
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Glycine o#idation to '02
Glycine roduced from serine or from the diet can also be o#idi/ed by $lycine
decarbo#ylase (also referred to as the $lycine clea!a$e comle#% G''* to yield a
second eui!alent of N%N1-methylene-tetrahydrofolate as &ell as ammonia and
'02.
'opy (romhttp://themedicalbiochemistrypage.org/amino-acid-metabolism.html
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Aromatic
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Aromatic
Amino
Acids
Phenylalanine Tyrosine Tryptophane
fumarate Aceto
acetate
Dopa &
Dopamine Melanine
Nor
epinephrin
&
epinephrine
Thyroxin
Satol &
!ndol Melatonin
Anthranilic Serotoninglucose etone
Alanine Nicotinamide
Acetoacetyl
"oA
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4iosynthesis of "yrosinefrom 5henylalanine
5henylalanine hydro#ylase is a mi#ed-function o#y$enase one atom of o#y$en is
incororated into &ater and the other into the hydro#yl of tyrosine. "he reductant is the
tetrahydrofolate-related cofactor tetrahydro#iopterin% &hich is maintained in the reduced
state by the 6AD+-deendent en/yme dihydroteridine reductase
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$yperphenylalaninemia - comlete deficiency of henylalaninehydro#ylase (lasma le!el of 5he raises from normal . to 2 m$7dL to
more than 2 m$7dL*.
"he mental retardation is caused by the accumulation of
henylalanine% &hich becomes a ma8or donor of amino $rous in
aminotransferase acti!ity and deletes neural tissue of 9-keto$lutarate.
Absence of 9-keto$lutarate in the brain shuts do&n the "'A cycle and
the associated roduction of aerobic ener$y% &hich is essential to
normal brain de!eloment.
6e&borns are routinelly tested for blood concentration of 5he.
"he diet &ith lo&-henylalanine diet.
Phenylketonuria
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A,AM9>,I,,A
SEMOGA +ERMAN