Amino Acid Catabolism

Amino Acid Catabolism Amino Acid Catabolism - Start

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Amino Acid Catabolism - Description

C483 Spring 2013. 1. Which . of the following is/are true statement(s) about . glutamine and alanine? . A) . They are . nitrogen . donors . in many biosynthetic reactions. . B) . They are part of the urea cycle. . ID: 205573 Download Presentation

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Amino Acid Catabolism




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Presentations text content in Amino Acid Catabolism

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Amino Acid Catabolism

C483 Spring 2013

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1. Which of the following is/are true statement(s) about glutamine and alanine? A) They are nitrogen donors in many biosynthetic reactions. B) They are part of the urea cycle. C) They carries nitrogen between tissues, thus avoiding high toxic levels of NH4+ in blood. D) In mammal liver, they receive net nitrogen from glutamate in transaminations.2. What would be the product of the transamination of the structure shown below? (The unionized forms are shown.)

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3. ATP is required to degrade many proteins because it is required toA) form the proteosome.B) attach ubiquitin to the target protein.C) hydrolyze a ubiquitinated protein.D) All of the above.4. The enzyme ________ is one of the most abundant in liver mitochondria and catalyzes the synthesis of the molecule shown below.A) arginase B) carbamoyl phosphate synthetase I C) 4-α-carbinolamine dehydratase D) transaminase 5. Which of the following is false concerning the urea cycle?A) Ornithine acts catalytically in the urea cycle.B) Metabolic disease can result from lack of urea cycle enzymes.C) The four reactions of the cycle take place in the liver mitrochondrial matrix.D) One molecule of urea is produced at the cost of 4 ATP equivalents.

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Overview

Protein TurnoverAmino Acid CatabolismNitrogen pathwaysCarbon backboneFrom perspective of human metabolism

Juicy Steak Part 2

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Digestion

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Protein Degradation

All proteins have a “half-life”Part of regulationAlso important in misformed/ mutant proteinsUbituitin

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Marked for destruction

Complex system guards against marking “good” proteinsCosts ATPProteasomeNucleophile hidden in barrel

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Amino Acid Degradation

Nitrogen processing is the first stepThen carbon chain is metabolizedExample:Two nitrogen transfer reactions

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Reaction1: Transamination

All amino acids shuttle their nitrogen toward glutamate

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Transamination

Not an overall Redox reactionRequires PLP

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Reaction 2: Oxidative Deamination

What happens to all the glutamate?Glutamate Dehydrogenase

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Nitrogen Processing on Tissue Level

The alanine-glucose cycle

Amino

Acids

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Nitrogen Processing on Tissue Level

Glutamine can act asAmmonia transporter (like alanine)Substrate in biosynthesis requiring amino groups

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Role of Liver Mitochondia

Sequester toxic ammoniaMake less toxic, execrable formUrea Cycle

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Carbamoyl phosphate

Cost of 2 ATPPhosphate leaving groupActivation of ammonia forExcretionbiosynthesis

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Chemistry of Urea Cycle

Catalytic ornithineFumarate Urea = 4 ATP

+ ATP

+ AMP

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Solving Metabolic Problems

Arginosuccinase deficiencyLow protein dietMinimize ammonium High arginine dietProvide carrier

X

excreted

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Urea Cycle: Compartmentalization

Ammonia locked into matrixUrea releasedUses glutamate/ aspartate shuttle

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Summary: Main Players

Glutamate: receives nitrogen from AA, then ammonia is released in liver mitochondria

Glutamine: ammonia transport; biosynthesis

Alanine: ammonia transport

Aspartate: nitrogen donor to urea

Arginine: urea cycle

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Answers

C

III

D

B

C


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