Metabolisme Senyawa N

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Protein Metabolism


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Protein DIGESTION & ABSORPTION

Proteolysis (lysis of proteins !ataly"e# byproteases

$ Proteases !lea%e pepti#e bon#s to

release free amino a!i#s or smallerpepti#e fra&ments

$ 'n#opepti#ases !lea%e internal pepti#e

bon#s$ 'opepti#ases !lea%e terminal pepti#e

bon#s


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)

Protein DIGESTION & ABSORPTION


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*!ti%ation of protein #i&estion en"ymes

$ Pepsinogen Pepsin+,l

-astri! ui!e


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Trypsinogen Trypsin

Chymotrypsinogen Chymotrypsin

Procarboxypeptidase A & B

carboxypeptidase A & B

Pancreatic Juice

enterokinase/

tripsin

Trypsis

Trypsis


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pe!ifi!ity of protein #i&estion en"yme

Enzyme Type Speciicity

Pepsin en#opepti#ase *romati! or leu!ine

rypsine 'n#opepti#ase Lysine or ar&inine

,ymotripsin 'n#opepti#ase aromati!

,arboypepti#ase * eopepti#ase ,teriminal aromati! or neutral

,arboypepti#ase B eopepti#ase ,terminal ar&inin or lysine

Leu!ineaminopepti#ase

eopepti#ase Nterminal leu!ine or neutral


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Protein !igestion & Absorption


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$ Tissue protein are constant"y being brokendo#n and resynthesized$

$ The %nitrogen or amino acid poo"% is a grandmixture o amino acids aai"ab"e in the ce""deried rom dietary sources or thedegradation o protein$

$ Since proteins and amino acids are notstored in the body' there is a constantturnoer o protein$

!()A*+C E,-+.+B+-* T0E1(

12 B1!( P1TE+)S


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$ Some protein is constant"y being

synthesized #hi"e other protein isbeing degraded$

$ Each day' some o the amino acids are

catabo"ized producing energy andammonia$ The ammonia is conerted to

urea and excreted rom the body and

represents a drain on the nitrogen poo"$


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!()A*+C E,-+.+B+-* T0E1(

12 B1!( P1TE+)S


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$ Purposes o amino acid degradation6 supp"y energy6 supp"y intermediates or synthesis o other

compounds6 remoe harmu" excess o certain amino

acids

A*+)1 AC+! *ETAB1.+S*


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$ *ost amino acids are irst stripped o theiramino group by t#o steps

3$ transamination ia 4"u transaminasetransers amino group to a"pha5ketog"utarate 6rom TCA cyc"e7 and orms4"u

8$ oxidatie deamination ia 4"udehydrogenase9 re:uires )A!;co5actorto oxidize the a carbon o the amino acid toreorm a5ketog"utarate9 a"so re"eases

ammonium ion 6)0


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Transamination


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4"utamate

!ehyrogenase


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!eamination


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7ter amino a!i# metabolism

). erine #ey#ratase6 Non oi#ati%e #eamination of Lserine

4. De!arboylations

6 Parti!ularly #e!arboylation of #amino a!i# toremo%e potential toi! of #amino a!i#

5. -lutaminase an# aspara&inase

6 u! &lutami! a!i# an# asparti! a!i# in tissues

is foun# not as te free a!i# but in !orespon#

ami#e (aspara&ine an# &lutamine


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Serine !ehydratase


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!ecarboxy"ationo 4"utamic acid

= 5A*+)1 B-T(+C AC+!


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Amino Acid 1xidases


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2)

The g"utaminase reaction proceeds essentia""y irreersib"y in the

direction o g"utamate and )0


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-EA C(C.E

Carbamyl phosphate

synthetase

9 2 *P

Ornithine

transcarbamylase

Argininosuccinate

synthetase

Argininosuccinase

Arginase

6key enzyme7


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The re"ationship o urea cyc"e to TCA


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The re"ationship o urea cyc"e to TCA

E)E4( -T+.+?AT+1) 21* A*+)1 AC+!S


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E)E4( -T+.+?AT+1) 21* A*+)1 AC+!S

Ab "iti A i A id * t b "i


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Abnorma"ities o Amino Acid *etabo"ism


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P-+)E CATAB1.+S*


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P(+*+!+)E CATAB1.+S*


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Metabolisme Senyawa N