Biosynthesis and Degradation of Nucleotides Lecture Review

A set of vocabulary flashcards covering the biosynthesis, regulation, and degradation of purine and pyrimidine nucleotides, related diseases, and pharmaceutical treatments.

De novo synthesis

The metabolic pathway that makes nucleotides from scratch.

Salvage pathways

Pathways that reutilize already made nitrogenous bases and nucleosides.

Nucleoside

A molecule consisting of a nitrogenous base combined with a 5 carbon sugar (ribose or deoxyribose).

Nucleotide

A nucleoside plus one, two, or three phosphate groups positioned at either the 5' or 3' position.

Purine

A heterocyclic classification of nucleotides featuring a double-ring structure.

Pyrimidine

A heterocyclic classification of nucleotides featuring a single-ring structure.

Pancreatic nucleases

Enzymes such as deoxyribonuclease and ribonuclease that break down DNA and RNA.

Nucleosidase

An enzyme responsible for the removal of the ribose sugar from a nucleoside.

Phosphatase

An enzyme responsible for the removal of phosphate groups from a nucleotide.

IMP (Inosine Monophosphate)

The parent molecule in the purine biosynthetic pathway that forms Adenine and Guanine.

Aspartate (Purine Synthesis)

The molecule that provides Nitrogen 1 in the structure of IMP.

Glutamine (Purine Synthesis)

The molecule that provides Nitrogen 3 and Nitrogen 9 in the structure of IMP.

Glycine (Purine Synthesis)

The molecule that provides Nitrogen 7 and Carbons 4 and 5 in the structure of IMP.

$$N^{10}\text{-Formyl-H}_4\text{folate}$$

Also known as $N^5, N^{10}\text{-Formyl-THF}$, it provides Carbons 2 and 8 in the structure of IMP.

Respiratory $CO_2$

The source of Carbon 6 in the structure of IMP which does not require biotin.

Ribose $5\text{-P}$

A starting molecule for purine synthesis obtained from the Pentose Phosphate Shunt.

PRPP (5-PhosphoRibosyl-1-PyroPhosphate)

An activated sugar molecule that requires ATP for its formation via PRPP synthetase.

PRPP synthetase

The enzyme that catalyzes the formation of PRPP from Ribose $5\text{-P}$ and ATP in the presence of $Mg^{+2}$.

Adenylsuccinate

An intermediate formed by the addition of aspartate to IMP during the conversion to AMP; requires GTP.

Xanthosine monophosphate

An intermediate in the conversion of IMP to GMP, requiring dehydrogenase and $NAD^+$.

PRPP aminotransferase

The enzyme that catalyzes the 1st committed step of de novo purine synthesis; it is low in the brain and absent in erythrocytes.

APRT (Adenine Phosphoribosyl Transferase)

The enzyme in the salvage pathway that converts Adenine plus PRPP into AMP and PPi.

HGPRT (Hypoxanthine-Guanine Phosphoribosyl Transferase)

The enzyme in the salvage pathway that converts Hypoxanthine or Guanine plus PRPP into IMP or GMP.

Xanthine oxidase

An enzyme that requires Mo and converts hypoxanthine to xanthine and xanthine to uric acid.

Uricemia

A condition characterized by increased levels of uric acid in the blood.

Podagra

Gouty arthritis specifically affecting the main joint of the big toe.

Allopurinol

A medication used to treat gout by inhibiting the enzyme xanthine oxidase.

Lesch-Nyhan Syndrome

An X-linked recessive disorder caused by HGPRT deficiency, resulting in gouty arthritis, mental retardation, and self-mutilation.

Von Gierke’s Disease

A Glycogen Storage Disease caused by Glucose-6-phosphatase deficiency that increases PRPP and uric acid production.

UMP (Uridine Monophosphate)

The parent molecule from which all pyrimidines (UTP, CTP, TMP) are formed.

Aspartate (Pyrimidine Synthesis)

The molecule that provides Nitrogen 1 and Carbons 4, 5, and 6 in the structure of UMP.

Glutamine (Pyrimidine Synthesis)

The molecule that provides Nitrogen 3 in the structure of UMP.

$CO_2$ (Pyrimidine Synthesis)

The source of Carbon 2 in the structure of UMP.

Carbamoyl Phosphate Synthetase II

A cytosolic enzyme used in pyrimidine synthesis that requires $CO_2$, glutamine, and 2 ATP.

Aspartate transcarbamoylase

The enzyme that catalyzes the committed step in pyrimidine synthesis, converting carbamoyl phosphate to carbamoyl aspartate.

Dihydroorotate

An intermediate in pyrimidine synthesis formed from carbamoyl aspartate with the release of $H_2O$.

CAD

A multifunctional enzyme complex involved in the initial steps of pyrimidine synthesis.

Orotic aciduria

A condition caused by defects in UMP synthase where orotic acid builds up in body fluids.

UMP synthase

A multifunctional enzyme required for the conversion of orotic acid and PRPP into UMP.

CTP synthetase

The enzyme that converts UTP to CTP using glutamine and ATP.

Thymidylate synthase

The enzyme targeted by FdUMP that catalyzes the conversion of dUMP to dTMP.

$$N^5, N^{10}\text{-Methylene-H}_4\text{folate}$$

The active form of folic acid used in methyl transfer reactions for the formation of dTMP from dUMP.

Methotrexate

A cancer drug and folate inhibitor that blocks the synthesis of $N^5, N^{10}\text{-Methylene-H}_4\text{folate}$.

FdUMP (Flurodeoxyuridylate)

A suicide inhibitor of the enzyme thymidylate synthase used in cancer treatment.

Ribonucleotide reductase

The enzyme responsible for forming deoxynucleotides by converting NDP to dNDP.

Flavr Savr Tomato

The 1994 GMO by Calgene designed to improve shelf life.

AquAdvantage salmon

A GMO fish that grows faster due to the incorporation of growth hormone DNA from another fish.

Inosine

A nucleoside produced during the degradation of adenosine before its conversion to hypoxanthine.

Alloxanthine

The metabolic product associated with the inhibition of xanthine oxidase by allopurinol.

Purine nucleoside phosphorylase

The enzyme responsible for converting adenosine to inosine and guanosine to guanine.