NUCLEOTIDE METABOLISM Flashcards
First purine derivative formed…
Inosine monophosphate (IMP)
Adenine nucleotides are components of 3 major coenzymes:
NAD+, FAD, Coenzyme A
Two products of IMP…
AMP and GMP
The activated form of ribose-5-phosphate.
5-phosphoribosyl-1-pyrophosphate (PRPP)
The enzyme needed to convert ribose-5-phosphate to PRPP.
PRPP synthetase
How many high energy phosphate equivalents are needed for the synthesis of PRPP?
Two. The reaction releases AMP from its original ATP state.
Major site of purine synthesis.
Liver
The following are required to synthesize IMP EXCEPT:
A. One mole of CO2
B. Two moles of formate
C. Two moles of glutamine
D. Two moles of glycine
D. Two moles of glycine
The primary requirement for the formation of GMP is _______, and AMP is ________.
ATP, GTP
The rate limiting steps in purine biosynthesis are:
⭕️ Synthesis of PRPP
⭕️ Amidotransferase reaction
The enzyme that catalyzes the second reaction in purine biosynthesis.
PRPP glutamyl amidotransferase
Uric acid is insoluble and is excreted in the urine as _____________.
Sodium urate crystals
The process in which free purine bases are reconverted to their corresponding nucleotides.
Phosphoribosylation
This reaction is catalyzed by what enzyme:
Adenine + PRPP AMP + PPi
Adenosine phosphoribosyltransferase or APRT
The following reactions are catalyzed but which enzyme of the salvage pathways:
Hypoxanthine + PRPP IMP + PPi
Guanine + PRPP GMP + PPi
Hypoxanthine-Guanine Phosphoribosyltransferase or HGPRT
A critically important enzyme of purine salvage in rapidly dividing cells is…
Adenosine deaminase or ADA
Deficiency in the enzyme that catalyzes the deamination of adenosine to inosine results in what disorder?
Severe combined immunodeficiency (SCID)
The synthesis of AMP from IMP and the salvage of IMP via AMP catabolism have the net effect of….
Deamination of aspartate to fumarate
This cycle is important in muscle cells.
Purine Nucleotide Cycle
The muscle-specific isoenzyme of AMP deaminase, and deficiencies in this enzyme leads to post-exercise fatigue, cramping, and myalgias.
Myoadenylate deaminase
The precipitation of urate maybe in the forms of:
⭕️ monosodium urate (MSU)
⭕️ calcium pyrophosphate dihydrate (CPPD)
Allopurinol strongly inhibits…
Xanthine oxidase
Results from the loss of functional HGPRT gene.
Lesch-Nyhan Syndrome
The net effect in Severe Combined Immunodeficiency Disease.
Inhibit DNA synthesis
Deficiency in glucose-6-phosphatase results in…
von Gierke disease
The carbamoyl phosphate used for pyrimidine nucleotide synthesis is derived from ___________ and ___________.
Glutamine and bicarbonate
Rate limiting enzyme of pyrimidine nucleotide biosynthesis..
Aspartate transcarbamoylase (ATCase)
The pyrimidine ring is synthesized from ______________ and ____________.
Carbamoyl phosphate and aspartate
N-donor of pyrimidine synthesis:
Glutamine
TRUE or FALSE: Pyrimidines are attach to PRPP for synthesis.
FALSE. They attached after the synthesis.
The first phosphorylation of UMP is catalyzed by:
Uridylate kinase
The second phosphorylation of UMP is catalyzed by:
Ubiquitous nucleoside diphosphate kinase
UTP is converted to CTP via CTP synthase through what process?
Amination
dUMP is converted to dTMP via what enzyme?
Thymidylate synthase
The action of dihydrofolate reductase is…
Regeneration of THF from DHF
ATCase prefers _______ as a substrate and is localized in the _________.
Glutamine, Cytoplasm
