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Block 3 Week 5 Meg > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

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1
Q

Synthesized in bacteria
Reduced form of folate
Transfers single carbon

A

Tetrahydrofolate (THF)

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2
Q

Synthesized from ATP + methionine
Transfers methyl groups
Alter transfer yields SAhcys then hcys

A

SAM

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3
Q

Transfers CO2

A

Biotin

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4
Q

Involved in oxidation reactions

A

Tetrahydrobiopterin

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5
Q

Cofactor in transaminase reaction
Coenzyme form of Vitamin B6
“Holds” the nitrogen

A

Pyridoxal Phosphate (PLP)

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6
Q

Total “ATP” generated from one round of the TCA cycle

A

12 ATP

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7
Q

Citrate inhibits (blank) and is an important component in (blank)

A

glycolysis; FA synthesis

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8
Q

Acetic acid from alcohol metabolism can enter the TCA cycle at this step

A

Acetyl-CoA + OAA –> Citrate

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9
Q

This complex is bound to the inner mitochondrial membrane

A

succinate dehydrogenase

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10
Q

What are methionine and cysteine both derived from?

A

homocysteine

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11
Q

What is tyrosine derived from?

A

phenylalanine

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12
Q

What is the reaction for glutamate synthesis? What enzyme catalyzes this reaction?

A

NH4+ + alpha-KG + NADPH + H+ –> glutamate + NADP+ + H20

Glutamate dehydrogenase

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13
Q

Glutamate synthesis is driven by toxic levels of free (blank). It occurs primarily in the (blank)

A

ammonia; liver

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14
Q

What enzyme takes Glutamate to Glutamine? What is required for this reaction?
What enzyme take Glutamine to Glutamate?
What is produced?

A

Glutamine synthetase
ATP + NH3
Glutaminase
NH4+

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15
Q

Does glutamate transport across cell membranes? Does glutamine?

A

NO; yes

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16
Q

Most abundant circulating amino acid

A

glutamine

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17
Q

(blank) is a Nitrogen donor for many synthesis reactions; (blank) allows transport of the detoxified form of NH4+

A

glutamine; glutamine

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18
Q

Discuss the glucose-glutamine cycle (starts with glucose in the muscle, ends with glucose in the kidney)

A

Glucose-

  • ->alpha-KG (glycolysis/TCA)
  • ->Glutamate (transaminase)
  • ->Glutamine (glutamine synthetase)
  • -> kidney
  • ->Glutamate (glutaminase)
  • ->alpha-KG (glutamate DH)
  • ->glucose (gluconeogenesis)
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19
Q

Equation for alanine synthesis; what enzyme is required for this reaction

A 
AA + pyruvic acid --> alpha-keto acid + alanine
alanine transaminase (ALT)
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20
Q

Transaminases are highly (blank) with a Keq = 1

Transaminases require what cofactor?

A

reversible

PLP

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21
Q

What can be used as a diagnostic for liver damage?

A

Serum ALT levels

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22
Q

Discuss the glucose-alanine cycle

A

In muscle:
Glucose –> pyruvate via glycolysis
Pyruvate –> alanine via alanine aminotransferase
In liver:
Alanine –> pyruvate via alanine aminotranferase
Pyruvate –> glucose via gluconeogenesis

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23
Q

What activates proteolysis of muscle protein to amino acids? Also activates transaminases and gluconeogenesis.

A

Cortisol

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24
Q

Aspartate synthesis; what enzyme is responsible for this reaction?

A

OAA –> ASP
Glutamate –> alpha KG
Glutamate-OAA transaminase (GOT)

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25
Asparagine synthesis; what enzyme is responsible for this reaction?
Aspartate --> asparagine Glutamine + ATP --> Glutamate asparagine synthetase
26
Do humans express asparaginase? Asparagine is often (blank) Some leukemia cells lack the ability to synthesize (blank) (blank) injections sometimes used for adult leukemia
NO glycosylated asparagine asparaginase
27
Serine synthesis
3 PGA --> SER | Glutamate + NAD+ --> alphaKG + NADH
28
The formation of serine has (blank) and (blank) intermediates, and generates (blank)
phosphopyruvate; phosphoserine; NADH
29
Glycine synthesis; what enzyme is responsible? What is required for this reaction?
Serine --> glycine via serine hydroxymethyltransferase | Requires THF --> N5, N10 methylene THF
30
Methionine synthesis; 2 things required for this reaction
homocysteine --> methionine Requires B12 Requires Methyl-THF-->THF
31
Cysteine synthesis
Methionine + ATP -- > SAM --> SAHcys --> homocysteine --> cystathione --> cysteine + alpha-aminobutyrate
32
What takes homocysteine to cystathionine? What does this require?
cystathionine synthase; PLP
33
What takes cystathionine to cysteine + alpha-aminobutyrate? What does this require?
cystathionase; PLP
34
What do deficiencies in cystathionine synthase or in cystathionase cause? What is this characterized by? What are treatments?
homocystinuria thinning/lengthening of long bones, osteoporosis, vascular thrombosis, mental deficiency dietary or vitamin treatments
35
Tyrosine synthesis; what enzyme catalyzes this reaction? What is required?
Phenylalanine --> tyrosine via phenylalanine hydroxylase | Requires tetrahydrobiopterine being oxidized to DHB
36
What can tyrosine be taken to via tyrosinase?
melanin
37
What can a build up of phenylalanine lead to? Symptoms? What is the treatment for this?
PKU; mental retardation, light skin color; dietary, no aspartame
38
Proline synthesis; what is required for this reaction?
Glutamate --> Proline | 2 NADH --> 2NAD+
39
Ubiquitin binds to (blank) residues on proteins destined for degradation. Ubiquitin can form chains - the (blank) the chain, the higher the signal for degradation.
lysine; longer
40
(blank) of protein determines RATE of ubiquination. Destabilizing N-terminal residues (blank) or (blank) = fast ubiquination. Stabilizing N-terminal residues (blank) or (blank) = slow ubiquination.
N-terminus arginine, leucine methionine, proline
41
(blank) sequences are also targets for degradation
P-E-S-T (proline-glutamate-serine-threonine)
42
Disease: formation of protein structures in neurons
Alzheimers and Parkinsons
43
Disease: rapid degradation of chloride channels
CF
44
Disease: Na+ channel in kidney not degraded, leading to excess Na+ absorption and early-onset hypertension
Liddle's syndrome
45
Amino acids that degrade to pyruvate
``` Alanine Cysteine Glycine Serine Threonine Tryptophan ```
46
Amino acids that degrade to acetyl-CoA
Isoleucine Leucine Threoine Tryptophan
47
defect in phenylalanine hydroxylase
PKU
48
defect in Tyrosine aminotransferase
tyrosinemia II
49
defect in homogentisate oxidase
alkaptonuria
50
defect in fumarylacetoacetate hydroxylase
tyrosinemia I
51
Amino acids that degrade to alpha-KG
``` Arginine Glutamine Histidine Proline Glutamate ```
52
Amino acids that degrade to OAA
Asparagine | Aspartate
53
Amino acids that degrade to Succinyl-CoA
Isoleucine Methionine Threonine Valine
54
Amino acid metabolism: most amino acids go to the (blank). What two amino acids are metabolized in intestinal mucosal cells? What type of amino acids leave the liver to go the muscle to be transaminated before returning to the liver?
liver; glutamate/glutamine; branched chain amino acids
55
When fasting, (blank) is a major source of amino acids. (blank) goes to the liver for gluconeogenesis. (blank) goes to kidneys and intestines.
muscle tissue; alanine; glutamine
56
List the steps in Phe degradation
Phe-->Tyr-->homogentisic acid int.-->fumarylacetoacetate int.-->acetoacetate
57
What enzyme takes Phe --> Tyr | What does a defect in this enzyme cause?
Phe hydroxylase; PKU
58
What takes Tyr to its homo intermediate | What does a defect in this enzyme cause?
Tyr aminotransferase; tyrosinemia II
59
What takes the homo int. to a fumaryl int? What does a defect in this enzyme cause?
homo oxidase; alkaptonuria
60
What enzyme takes fumaryl int to acetoacetate? What does a defect in this enzyme cause?
fumaryl hydroxylase; tyrosinemia I
61
What other amino acids degrade to acetyl-CoA?
Isoleucine Lysine Threonine Tryptophan
62
To take histadine to Glutamate and ultimately to alpha-KG, how many steps are involved? If there is a defect in histadase (the first step), what does this cause? If there is a folate deficiency, what accumulates?
4; histidinemmia; formimino glutamic acid (FIGLU)
63
What other amino acids get degraded to glutamate and ultimately alpha-KG?
Arginine Glutamine Histadine Proline
64
What takes serine to cystathione? What takes homocysteine to cystathione? (same enzyme) What does a defect in this enzyme cause?
cystathionine synthase; homocystinuria
65
What takes glycine to CO2 and NH4+? What does a defect in this enzyme cause?
glycine cleavage enzyme; nonketotic hyperglycinemia
66
What enzyme takes glycine to glyoxylate? What does a defect in this enzyme cause?
glycine transaminase; oxaluria type I
67
Discuss the degradation of asparagine to OAA
asparagine --> aspartate --> OAA
68
What does a defect in branched chain alpha-keto acid dehydrogenase complex cause?
maple syrup urine disease
69
Degradation of (blank) goes through homocysteine, propionyl-CoA, methylmalonyl-CoA, and ultimately Succinyl-CoA. What takes methylmalonyl-CoA to Succinyl-Coa? What does a defect in this enzyme cause?
methionine; methyl-malonyl CoA mutase (requires B12); methylmalonic aciduria
70
What other amino acids degrade to succinyl-Coa?
Isoleucine Methionine Threonine Valine
71
Missing enzyme Dihydropteridine reductase - causes accumulation of phenylalanine. What does this cause?
PKU (non-classical)
72
1st step in urea cycle
CO2 + NH4+ --> Carbamoyl phosphate (via Carbamoyl-phosphate synthetase)
73
A build up of carbamoyl phosphate leads to (blank) in urine
orotate
74
List the steps of the urea cycle
``` Carbamoyl phosphate Citrulline Arginosuccinate Arginine Ornithine ```
75
How many ATP does the urea cycle require?
4 ATP
76
What two intermediates in the cycle are in the mito matrix?
ornithine --> citrulline
77
Blood urea level measured as (blank). This rises sharply (uremia) in renal failure
BUN
78
Bacterial enzyme (blank) can cleave urea, alkalinizing the urine causing precipitation of magnesium ammonium phosphate -> kidney stones
urease
79
Inherited defects of urea cycle enzymes lead to (blank) and encephalopathy. Feeding difficulties, vomiting, lethargy, irritability, aversion to protein rich foods. (blank) deficiencies because α-ketoglutarate is converted to glutamine. (blank) levels elevated as well as immediate substrate of deficient enzyme
hyperammonemia (lots of NH4+); ATP; glutamine
80
``` Therapy for urea cycle enzyme deficiencies: Limit (blank) intake Remove excess (blank) Replace intermediates Liver transplant ```
protein; ammonia
81
The urea cycle is related to this component of the TCA cycle, and shares argino-succinate as an intermediate
aspartate-arginosuccinate shunt
82
Three steps that require a transaminase
3PGA --> serine Pyruvate --> alanine OAA --> Aspartate
83
Three steps that require NH4+
alpha KG --> glutamate glutamate --> glutamine/proline/arginine aspartate-->asparagine

Block 3 Week 5 Meg (8 decks)

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