Kategorier: Alle - feedback - enzymes - degradation - nucleotides

av Zohrab Ajani 9 år siden

318

Block 4 Young Review

The text discusses the synthesis and degradation pathways of purines and pyrimidines, essential components of nucleotide metabolism. It details the enzymatic processes involved in purine production, including the conversion of ribose 5-phosphate to phosphoribosyl pyrophosphate (

Block 4 Young Review

Nucleotide Metabolism Synthesis of Purines & Pyrimidines

Pyrimidine Production

Degradation
ALL ARE water soluble ==> NO KIDNEY STONES
Thymine --> CO2, NH4+ and beta-aminoisobutyrate
Uracil --> CO2, NH4+ and beta-alanine
Cytosine ---> de-aminated ===> Uracil
Production
Salvaging

Nucleotides ------phosphorylase-----> nucleosides

Glutamine + CO2 + 2ATP ----> Carbamoyl Phosphate

Enzyme: (CPS-II) Carbomoyl Phosphate Synthase II

POS Feedback: PRPP

NEG FeedbacK: UTP

Purine production

Ribonucleotide Reductase (RR)
Regulation:
Nucleotides -------> deoxynucleotides
Nucleosides ----> uric acid
Excess uric acid ----> GOUT!
Via slavaging dietary nucleotides Nucleotides ---> nucleosides
Inosine ---->Hypoxanthine -----> Xanthine -----Xanthine oxidase--------> Uric Acid

Allopurinol inhibits xanthine oxidase! => less uric acid --> less gout!

Adenosine -------adenosine deaminase-------> Inosine

When broken down = SIDS "bubble boy"

Hypoxanthine ------HGPRT-----> IMP

When broken down = Lesch–Nyhan Disease

Adenine ---APRT----> AMP

when broken down = Kidney Stones

Negative Feedback
GDP and ADP inhibit -->

PRPP synthase

AMP inhibits-->

Adenylosuccinate synthase

GMP inhibit -->
GMP, GDP, & GTP inhibit--->AMP, ADP, & ATPinhibit--->

Glutamine phosphoribosyl amindotransferase

Purine Nucleotide Cycle in muscle cells
Releases NH3
IMP + Aspartate ===> AMP + Fumarate
IMP + ATP + Glutamine ==> GMP
IMP + GTP + Aspartate ==> AMP
PRPP + GLUTAMINE -------> IMP
IMP dehydrogenase

inhibited by mycophenolic acid

IMP is "branch point" b/t ATP and GTP synthesis
Enzyme Glutamine Phophoribosyl Amino Transferase
Ribose 5-P + ATP -----> PRPP
Enzyme PRPP Synthetase