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DEMS > Proteins III > Flashcards

Proteins III Flashcards

1
Q

Sulfur aa

A

cysteine

methionine - essential

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2
Q

cysteine can form disulfide crosslinks with another cysteine to form

A

cystine

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3
Q

Methionine degradation –> cysteine synthesis

PATHWAY?

A

MET –> SAM –> SAH –> HOMOCYSTEINE –> CYSTATHIONE –> CYSTEINE

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4
Q

What amino acid is included in the synthesis of cysteine from methionine (complexed with homocysteine?)

A

serine

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5
Q

We can also regenerate methionine from homocysteine - what two coenzymes are required for this?

A

THF

VitB12

The methyl group is transferred from THF to B12 to homocysteine

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6
Q

Enzyme important in initial production of cysteine from homocysteine?

A

cystathione-Beta-synthase
this enzyme makes cystathione - an intermediate - and requires VitB6 derivative PLP

Mutations can lead to hyperhomocysteinemia or homocystinuria

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7
Q

hyperhomocysteinemia can be due to?

A

low levels of folate, B6, or B12

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8
Q

Hyperhomocyteinemia can lead to

A

vascular disease

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9
Q

Folate, B6, and B12 are all important in methionine breakdown via homocysteine metabolism, but which are important for regenerating methionine and which are important for generating cysteine

A

B12 and folate are important for regenerating methionine

B6 is important for generating cysteine

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10
Q

defect in cystathionine beta-synthase leads to?

A

mental retardation, osteoporosis, and vascular disease

cysteine becomes essential

can treat with B6 if residual activity to try and force

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11
Q

Cysteinuria -

A

kidney stone and renal failure due to defect in transporter of cysteine which leads to crystallization

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12
Q

cysteinuria treat with

A

acetazolamide - makes cysteine more soluble

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13
Q

treat homocystinuria with?

A

B6 to force

and cysteine become essentia

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14
Q

treat hyperhomocysteinemia with?

A

B12 and folate and B6

cysteine become essential

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15
Q

plasma levels of homocysteine are directly correlated with?

A

CV mortality

associated with vascular disease - pro-inflammatory

impaired wound healing

cancer (Cervical)

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16
Q

SAM is similar to

A

ATP

energy storage unit

17
Q

SAM has charged what?

A

charged sulfur that is highly reactive

methyl donor

18
Q

We know SAM is a methyl donor, what important hormone does it methylate to yield other important hormone

A

methylates norepinephrine –> epinephrine

19
Q

We know SAM is a methyl donor, which base does it methylate?

A

cytosine residues in DNA - important for epigenetics

20
Q

SAM is a methyl-donor - who else is a methyl donor (hint: derivative of micro-nutrient)

A

THF

21
Q

What is the name of the enzyme that produces THF from folate?

A

dihydrofolate reductase (DHFR)

22
Q

Why would an oncologist be interested in the enzyme dihydrofolate reductase (DHFR)

A

Because methotrexate (A cancer medication) inhibits this enzyme and thus inhibits the formation of THF from folate - THF is important in DNA synthesis so block cell proliferation

23
Q

Glutathione (GSH) who is in the middle

A

cysteine - with its lovely sulfur

24
Q

What does GSH do?

A

redox buffer
keeps Fe in Fe2+ state (active hemaglobin)
protects against ROS
Cofactor for muchos enzymes
enables proper disulfide bridge formation (Along with PDI)

25
Q

Glutathione peroxidase

A

Mutations lead to high BC risk

26
Q

Glutathione reductase

A

Mutations problematic for heme

27
Q

Glutathione S-transferase - conjugates to other agents

A

Detox (ROS)

Upregulated in tumors

28
Q

Trp metabolism

A

pyruvate or acetyl-CoA

29
Q

Trp makes?

A

seratonin
melatonin
niacin (b3)

30
Q

Trp cofactor

A

BH4

31
Q

Phenylalanine hydroxylase mutations –>

A

phenylketonuria

32
Q

PKU toxic byproducts

A

phenylpyruvate
phenylacetate
phenyllactate

33
Q

Tyrosine yields?

A

catecholamines (NTs)

melanin

34
Q

Errors in tyrosine metabolism can lead to?

A

Parkinson
Depression
Albinism

35
Q

Parkinson’s treat with Dopa and MAOs why?

A

Because MAO breaks down catecholamines (DOPA, Dopamin, Norepi, Epi, serotonin)

36
Q

Decarboxylation of numerous amino acids –>

A

biological amines (serotonin, catecholamines, GABA, Histamine)

DEMS (21 decks)

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