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Flashcards in Biochem Deck (29):
1

What amino acids are necessary for purine synthesis?

Glycine (carbon)
Aspartate (nitrogen)
Glutamine (nitrogen)

(also need CO2 and THF)

2

What is the rate limiting step of purine synthesis?

Glutamine PRPP amidotransferase

3

What drugs inhibit glutamine PRPP amidotransferase?

6-mercaptopurine
Azathioprine (6-MP prodrug)

4

What type of drug is azathioprine?

Azathioprine is an immunosuppressant

5

What are some possible toxicities of azathioprine?

Leukopenia
Anemia
Thrombocytopenia

6

What enzyme degrades 6-MP?

Xanthine oxidase...allopurinol inhibits this enzyme...FYI

7

When is 6-MP used?

Leukemia
IBD

8

What is needed for pyrimidine synthesis?

Aspartate
Carbamoyl phosphate
THF

9

What is the rate limiting step of pyrimidine synthesis?

Carbamoyl Phosphate Synthetase II (CPS 2)

Requires ATP

10

UMP synthase is another necessary enzyme in pyrimidine synthesis. What happens when this enzyme is deficient?

Orotic Aciduria

11

What are the signs of orotic acuduria?

Increased orotic acid in urine
Normal urine ammonia level
Megaloblastic anemia that is NOT cured with folate/B12

12

Ribonucleotide reductase is the enzyme that puts the d in dna. What drug inhibits this enzyme?

Hydroxyurea

13

When is hydroxyurea used?

CML
Skin cancer
Sickle cell disease (increases HbF)

14

What are the side effects of hydroxyurea?

Bone marrow suppression
GI upset

15

What drug inhibits the methylation of dUMP to dTMP?

5-Fluorouricil (5-FU)

Flucytosine gets converted to 5-FU

16

When is 5-FU used?

Colon cancer
Pancreatic cancer
Basal cell carcinoma

17

What are the side effects of 5-FU?

Myelosupression
Photosensitivity

18

When is flucytosine used?

Systemic fungal infections...given with amphotericin B

19

DHFR is also necessary for the methylation of dUMP. What drugs inhibit DHFR?

Methotrexate (humans)
Trimethoprim (bacteria)
Pyrimethamine (protozoa)

20

What enzyme is necessary for the conversion of adenosine to inosine (for the purine salvage pathway)?

Adenosine deaminase (ADA)

21

What is the metabolic effect of ADA deficiency?

A build up of ATP and dATP causes a feedback inhibition on ribonucleotide reductase...NO DNA synthesis

22

What is the medicinal effect of ADA deficiency?

SCID (No B cells or T cells)
Chronic diarrhea
FTT
No thymic shadow on CXR

23

Lesch-Nyhan syndrome is a purine salvage disease. What enzyme is deficient with this disease?

HGPRT

24

What are the s/s of Lesch-Nyhan syndrome?

"HGPRT"
H- Hyperuricemia
G- Gout
P- Pissed off (aggression, self-mutilation)
R- Retardation (intellectual disability)
T- dysTonia

25

What cancer gene includes a MMR mutation?

HNPCC

26

What is an effect of mutated NER?

Xeroderma pigmentosa

(easy to remember because UV rays cause thymine dimers...and NER fixes thymine dimers)

27

What syndrome is caused by a helicase mutation?

Bloom syndrome

28

What process is mutated with ataxia telangiectasia?

NHEJ

29

BRCA1&2 are mutations in what process?

dsDNA break repair