Biochemistry Wk 11- LOOK AT PPT Flashcards
Degradation in the small intestine
• Ribonucleases and deoxyribonucleases
• phosphodiesterases
• nucleotidases
• nucleosidases
• urate oxidase
PURINE NUCLEOTIDE DEGRADATION
Degradation of dietary nucleic acids occurs in the small intestine, where pancreatic nucleases hydrolyze them to nucleotides.
The nucleotides are sequentially degraded by intestinal enzymes to nucleosides, phosphorylated sugars, and free bases.
Uric acid formation
[1] An amino group is removed from AMP
by AMP deaminase and from adenosine by adenosine deaminase.
[2] IMP and GMP are converted into their respective nucleoside forms, inosine and guanosine, by the action of 5′-nucleotidase.
[3] Purine nucleoside phosphorylase converts inosine and guanosine into their respective purine bases, hypoxanthine and guanine.
[4] Guanine is deaminated to form xanthine.
[5] Hypoxanthine is oxidized by XO to xanthine, which is further oxidized by XO to uric acid, the final product of human purine degradation. Uric acid is excreted primarily in the urine.
GOUT- symptoms and treatment
Asymmetric joint distribution. Joint is swollen, red and painful.
- painful big toe
-Tophus formation (often on external ear)
- active attack tends to occur after a large meal with foods rich in purines (red meat, seafood), trauma, surgery, diuresis, alcohol consumption
TREATMENT-
Glucocorticoids, colchinne
Xanthine oxidase inhibitors ( allopurinol, febuxostat)
Athrocentesis
Joint aspiration is a procedure whereby a sterile needle and syringe which are used to drain fluid from a joint
Can help define arthritis, gout etc…
Adenosine deaminase deficiency
• ADA is expressed in a variety of tissues, but, in humans, lymphocytes have the highest activity of this cytoplasmic enzyme.
• A deficiency of ADA results in an accumulation of adenosine, which is converted to its ribonucleotide or deoxyribonucleotide forms by cellular kinases.
• As dATP levels rise, ribonucleotide reductase is inhibited, thereby preventing the production of all deoxyribose-containing nucleotides.
• Cells cannot make DNA and divide.
• The dATP and adenosine that accumulate in ADA deficiency lead to developmental arrest and apoptosis of lymphocytes.
Adenosine delaminase deficiency
B and T cell disorders
IL- 2R gamma chain
Demaminase deficiency
Failure to thrive, chronic diarrhoea, recurrent viral,bacterial, fungal, protozoan infections
Decrease T cell receptor excision circles
Absence of thymine shadow,
Germinal centres (lymph node biopsy)
T cells (flow cytometry)
PYRIMIDINE SYNTHESIS
The sources of the atoms in the pyrimidine ring are glutamine, CO2, and aspartate
The de novo synthesis of pyrimidines occurs in the cytoplasm beginning with aspartate,co2, and glutamine. A Carbamoyl phosphate synthetase creates carbaamoyl phosphate
