12/1 - Purines and Pyrimidines

nitrogenous base, pentose sugar, phosphate

What are the three essential components of a nucleotide?

Purine, Pyrimidine

What are the two types/categories of nitrogenous bases?

Purine

Which type of nitrogenous base includes adenine/guanine and has 2 rings?

Pyrimidines

Which type of nitrogenous base includes uracil, thymine, and cytosine and has 1 ring?

tRNA, viral DNA

In what two molecules are modified nucleotides found?

B-N-glycosidic

What type of linkage joins pentose sugars to nitrogenous bases?

OH

What group is present on the 2 carbon of a ribose nucleotide?

H

What group is present on the 2 carbon of a deoxyribonucleotide?

PRPP

From what molecule are the sugar and phosphate donated in nucleotide synthesis?

de novo, salvage

What are the two pathways of purine synthesis?

cytoplasm

In what cellular location are the enzymes needed for purine synthesis located?

PRPP

What molecule is formed in the first step of purine synthesis de novo? It is made by PRPP synthetase.

PRPP synthetase

What enzyme is the first step of de novo purine synthesis, making PRPP, and is inhibited by ATP/GTP?

GPAT

What enzyme is the second step of purine de novo synthesis, is the rate-limiting step, and makes 5-phosphoribosylamine from PRPP? It is inhibited by AMP, GMP, and IMP and activated by glutamine and PRPP.

Glutamine, PRPP

What two molecules activate the rate-limiting step (GPAT) of purine de novo synthesis? One of them is feedforward control.

IMP

What molecule is formed by the third step of purine de novo synthesis in a sequence of 9 reactions?

adenylosuccinate synthetase

What enzyme is the fourth step of de novo purine synthesis, turns IMP to AMP, is inhibited by AMP, and needs GTP to work?

GTP

What energy molecule is needed to activate adenylosuccinate synthetase in purine synthesis?

AMP, GMP

What two molecules can be made from IMP in the fourth step of purine synthesis?

GMP synthetase

What enzyme forms GMP from IMP in the fourth step of purine synthesis, needs ATP, and is inhibited by GMP?

PABA

From what molecule is folate made from in bacteria?

Sulfa, trimethoprim

What two drug groups are used to inhibit bacteria folate synthesis?

Diet

From what do humans get folate as a vitamin?

folic acid

What vitamin is the most common deficiency worldwide and leads to birth defects and anemia?

HGPRT, APRT

What are the two enzymes involved in purine salvage synthesis?

APRT

Which enzyme in salvage pathway converts adenine to AMP?

HGPRT

Which enzyme in the salvage pathway converts hypoxanthine and guanine to IMP and GMP?

Yes

Are the amounts of AMP/GMP and purines/pyrimidines kept equal in the body?

Leesch nyhan

What is the syndrome that results from deficiency of HGPRT? It leads to fewer purines, no salvage pathway, and increased uric acid, orange crystals, and behavioral disturbances.

HGPRT

Leesch nyhan syndrome results from a lack of which enzyme in the purine salvage pathway?

xanthine oxidase

What enzyme is used in purine degradation to convert both hypoxanthine and guanine to xanthine? This leads to uric acid formation and buildup causes gout.

Allopurine

What is the term for the drug to treat gout that inhibits xanthine oxidase, preventing uric acid buildup?

Adenosine

Which is the only whole purine that is recycled?

adenosine kinase

What is the term for the enzyme which is used to recycle adenosine to make AMP? Inhibition of the enzyme is used in pain management.

Pyrimidine

Synthesis of which nucleotide group is only de novo, with no salvage pathway, and the rings are made before being attached to the ribose phosphate?

CAD

What is the term for the enzyme that does the first three steps of the pyrimidine synthesis pathway?

CPS II

What is the term for the enzyme that does the second and rate-limiting step of the pyrimidine pathway? It makes carbamoyl phosphate from glutamine and CO2.

Glutamine, CO2

What two things are used by CPS II to make carbamoyl phosphate in the pyrimidine pathway?

No

Is folic acid required in pyrimidine synthesis?

UTP

What molecule inhibits CPS II activity in pyrimidine synthesis?

ATP, PRPP

What two molecules activate CPS II activity in pyrimidine synthesis?

ASP transcarbamoylase

What is the term for the regulated domain/enzyme of bacterial pyrimidine synthesis?

UMP Synthase

What is the term for the enzyme composed of OPRT and OMP decarboxylase domains, deficiency of which leads to increased orotic acid in blood and urine? It also leads to decreased pyrimidine formation and RBC formation, megaloblastic anemia and decreased DNA synthesis and cell division.

Orotic aciduria

What is the term for the condition in which UMP Synthase is deficient, leading to buildup of a molecule in blood and urine, as well as decreased cell division and RBC formation?

RBC

Which type of cell specifically has its formation inhibited in the orotic aciduria/UMP synthase deficient condition?

CTP synthetase

What enzyme converts UTP to CTP, using an N donated by glutamine and a ribose sugar? The UTP is gained from monophosphate and nucleoside diphosphate kinase activities.

ribonucleotide reductase

What is the term for the enzyme that converts ribose to deoxyribose in order to keep concentrations of them equivalent? It happens during S phase of the cell cycle and is inhibited by hydroxyurea and dATP.

Thioredoxin reductase

What enzyme is used to restore thioredoxin during cell division using NADPH?

Thymidylate synthase

What is the term for the enzyme which converts dTMP to dUMP? It uses THF and is inhibited directly by fluorouracil and indirectly by MTX.