Lecture9-AMINOACIDMETABOLISMPART2 Flashcards by Daniella Andre

What are the fates of arginine?

Protein synthesis, nitric oxide, creatine, L-ornithine and agmatine

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What is the precursor of ornithine in intestinal arginine metabolism ? taken place where?

Glutatmate
mitochondria

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What two precurors of ornithine?

Glutamate (in mitochondrion) and arginine (in cytosol)

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Citrulline comes from where?

Ornithine and carbamoyl phosphate (urea pathway)

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What is the fate of citrulline? with what enzyme and other factor? ?

Fate: arginino-succinate

Enzyme and factor: Arginiosuccinate synthetase and aspartate

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What is the fate of argininosuccinate?

Arginine to then go to ornithine

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What is the nitric oxide synthase reaction?

Arginine to citrulline and NITRIC OXIDE with nitric oxide synthase (eNOS)

Also called citrulline NO cycle
**the e is for endothelial

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What is NO?

It is a signaling molecule to allow relaxation in muscle

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Where and when is arginiosuccine synthetase (AS) used?

LIVER: in the urea cycle, AS is used to take citrulline to argininosuccinate to then be later converted to UREA
*** get rid of NH4+

KIDNEY : AS is used to take citrulline to agininosuccinate to later be created to arginine

ENDOTHELIUM: in the citrulline-NO cycle, AS is used to take citrulline to argininosuccinate to later make NO

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Arginine can turned to omithine with what enzyme and what is released (think urea cycle)?

Arginase and releases urea

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In creatine biosynthesis what is the precursor of creatine?

arginine

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Where is creatine created?

In the liver

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What happens after the creation of creatine

In the muscles, creatine phosphate is created with the help of ATP and creatine phosphokinase

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Now overall what are ALL the ‘products’ of arginine

Ornithine and urea
NO
creatine

Arginine can help with the formation of proline with glutamate

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What is the precursor of glutamate

histidine

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Glutamate can form what?

Proline

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What can help glutamate to make proline

arginine

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What is the precursor of tyrosine

phenylalanine

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What are the fates of tyrosine

Thyroid hormones (thyroid)

Catecholamines (adrenals, CNS)

Melanine (e.g. skin)

Fumarate and acetoacetate (liver)

Example the whole phenylalanine hydroxyase reactions

7,8- dihydrobiopterin is reduced by dihydrobiopterin reductase (with NADH) to produce 5,6,7,8-tetrahydrobipterin (THIS IS THE COFACTOR)

5,6,7,8-tetrahydrobipterin and the enzyme phenylalanine hydroxylase (with O2) is used to take phenylalanine–>tyrosine

What happens when we do not have enough 5,6,7,8-tetrahydrobipterin

We will not convert phenylalanine–>tyrosine effectively

What is needed with dihydrobiopterin reductase?

NADH+H to go to NAD+

What is needed for Phenylalanine hydroxylase besides 5,6,7,8-tetrahydrobipterin?

Oxygen

A deficiency in Phenylalanine hydroxylase and dihydrobiopterin reductase causes what?

PKU

Which enzyme is deficient in TRADITIONAL PKU patients?

Phenylalanine hydroxylase

Which enzyme is deficient in ATYPICAL PKU patients?

dihydrobiopterin reductase

What is the solution to the enzyme deficiency in PKU patients ?

Saproterin=Kuvan which is an analog of 5,6,7,8-tetrahydrobipterin so it can bypass the cofactor and make tyrosine avoid Phenylalanine which is in aspartame (sweetener) in soft drinks

What are symptoms in PKU patients?

Neurological issues

How does PKU cause neurotoxicity ?

Phenylalanine interfere with the hydrophobic amino acid transport across Blood brain barrier, COMPETING for the SAME active transport system as LEUCINE, component of MYELIN Phenylpyruic acid is a competitive inhibitor of pyruvate dehydrogenase (PDH) complex, PDH complex is essential in synthesis of fatty acids and cholesterol thus an increase in phenylpyruvic acid contributes to lack of myelin formation

What is the precursor of tyrosine

Phenylalanine

What is the fate of tyrosine ?

dopamine, norepinephrine and epinephrine

What is the Rate limiting step of the formation of dop, nor, and epinephrine from tyrosine?

Tyrosine hydroxylase

More specific, what is the precursor of dopamine ? what enzyme?

DOPA DOPA decarboxylase--> release CO2

What inhibits DOPA decarboxylase ?

carbidopa

What is another fate of tyrosine besides dope, nore, epi?

Pheomelanine (red pigments) and eumelanins (black pigments) Thyroid hormones

what is the enzyme used to make pigments? what happens if we inhibit this ?

tyrosinase (cu+2) Albinism

What is the precursor of thyroid hormones

tyrosine

NOW, what are ALL THE FATES FOR TYROSINE

thyroid hormones Pheomelanine (red pigments) and eumelanins (black pigments) DOPA to dopamine, norepinephrine, epinephrine

What is the fate of tryptophan

Serotonin, Nicotinate (niacin), Melatonin Indoleacetate (not highlighted on her slide)

What is the rate limiting step used to take tryptophan to serotonin

Tryptophan 5-hydroxylase

Serotonin is a neurotransmitter that is responsible for what?

responsible for exerting inhibitory control over impulsive behavior

besides tryptophan what can help form melatonin? (lower yield)

serotonin

What is the fate of nicotinate (niacin)? lower yield

NAD and NADP

In a different slide, she used stated another precursor (besides serotonin) is what?

5-hydroxytryptophan

Just in case she does not use serotonin, what is the chemical name of serotonin?

5-hydroxytrptamine