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Amino Acid Metabolism
10/11/11 Fourth Lecture
19
Medical
Graduate
10/12/2011

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Cards

Term
What are the two main classes of amino acids and how are they divided?
Definition
1. Essential and Non Essential

2. Essential must come from diet or protein degradation, non essential can be synthesized in mammals
Term
What is the cofactor involved in aminotransferases, where does it come from, and what purpose does it serve?
Definition
1. Pyridoxal phosphate
2. Derivative of vitamin B6
3. Shuttle point for amino group in transferring process
Term
What enzyme converts phenylalanine to tyrosine? What is the essential cofactor?
Definition
1. Phenylalaine hydoxylase

2. BH4

Note: BH4 goes to BH2 and is reconverted by NADH to BH4
Elevated Phe caused by problems in this pathway lead to altered brain function
Term
What are some of the roles of tyrosine?
Definition
1. Make melanin
2. Synthesize catecholamines (again, uses BH4)
3. Degrade to fumarate and aceto acetate
Term
What is the disorder called when Phenylalanine cannot be converted to Tyrosine?
Definition
Phenylketonuria
Term
What is the universal first step in amino acid degradation?
Definition
Removal of alpha amino group
Term
What are the two classes in terms of whether degraded amino acids can be used for gluconeogenesis or not? What determines what type they are?
Definition
1. Glucogenic or ketogenic

2. Where their carbon skeleton breakdown product falls in the TCA cycle. If its acetoacetate or acetyl CoA, carbons will be burned off in the TCA cycle and it is ketogenic. Any other intermediate (pyruvate, alpha ketoglutarate, oxaloacetate, fumarate, succinyl CoA) are glucogenic
Term
What are the 3 branched chain amino acids?
Definition
Leucine, isoleucine, and valine

Note: all are essential AA
Term
How do branched chain amino acids enter the mitochondrion? What types of activity happens here?
Definition
BCATm - branched chain amino acid aminotransferase

Converts AA to alpha keto acids upon pumping them into the mitochondria
Term
What enzyme breaks down the branched chain alpha keto acids into TCA cycle components?
Definition
Branched Chain alpha keto acid dehydrogenase
Term
What are the 3 potential end products of the breakdown of branched chain amino acids?
Definition
Succinyl CoA (glucogenic)
Aceytl CoA (ketogenic)
Acetoacetyl CoA (ketogenic)
Term
What is maple syrup urine disease?
Definition
A deficiency in the branched chain alpha keto acid dehydrogenase enzyme (BKCD)

Leads to a buildup of leucine, isoleucine, valine, and their alpha keto acids in the blood

Gives urine characteristic odor and leads to mental retardation
Term
Where does THF (Tetrahydrofolate) come from and what is its function?
Definition
1. Breakdown of Glycine by Glycine Cleave complex, as well as conversion of folic acid by dihydropholate reductase (needs NADPH)

2. THF is a critical molecule capable of donating individual carbons in reactions

Note: Absence of Glycine Cleavage Complex leads to nonketotic hyperglycinemia
Term
What is SAM, what is it synthesized from, and what is its role?
Definition
1. S-adenosylmethione

2. Synthesized from methionine (via SAM synthetase)

3. It is the MAJOR methy group donor in one carbon metabolism
Term
What is the end product of SAM reactions and what is its importance?
Definition
SAM produces SAH

SAH is toxic and needs to be reconverted to Cysteine or Methionine
Term
What is serotonin synthesized from? What is the cofactor?
Definition
1. Tryptophan

2. BH4
Term
What are catecholamines synthesized from? What are the cofactors? What is the rate limiting step?
Definition
1. Synthesized from Tyrosine

2. BH4, B6, Vit C, and SAM are the cofactors

3. Rate limiting step is dehydroxylation of Tyrosine with BH4 as a cofactor
Term
What amino acids are involved in the synthesis of creating? What is the committed step?
Definition
1. Arginine, Methioning, Glycine

2. Breakdown of Glycine to ornithine and guanidinoacetate is the committed step
Term
What amino acids are involved in the synthesis of creating? What is the committed step?
Definition
1. Arginine, Methioning, Glycine

2. Breakdown of Glycine to ornithine and guanidinoacetate is the committed step
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