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Fun I Exam 2 C

Nucleotide Synthesis and Degradation & DNA

Purine degradation: significant activity occurs in the _____ digestive tract **because all natural foods that we consume have nucleotides in them
Nucleotides are first converted to nucleoSIDES by intracellular ____ Nucleosides are then degraded by _____ These products are converted to XANTHINE by ____ and ____ nucleotidases (under strict regulation to ensure substrates (often intermediates) are not depleted below critical levels Purine nucleoside phosphorylase (PNP) Guanine deaminase & xanthine oxidase
Purine degradation: inosine ---> hypoxanthine Purine nucleoside phosphorylase (PNP)
Purine degradation: hypoxanthine (or PNP product) ---> uric acid xanthine oxidase **target enzyme for gout treatment to prevent production of uric acid
Purine degradation: AMP ---> ? ---> ? ---> ?... AMP ---> IMP ---> Inosine OR AMP ---> Adenosine ---> Inosine **can be deaminased and dephosphorylased in either order Inosine ---> Hypoxanthine ---> uric acid
How many enzymes from IMP --> AMP? How many enzymes from AMP --> IMP? IMP --> AMP = two enzymes (when making nucleotides AMP --> IMP = one enzyme (when breaking down nucleotides)
Oxidizes hypoxanthine to uric acid in liver, intestines (and milk) xanthine oxidase
Humans and other primates excrete ____ in the urine but most N goes out as ____ Birds, reptiles and insects excrete ____ as their major N excretory compound Uric acid Urea (MOST for humans and primates) Uric acid (MOST for birds, reptiles)
Gout occurs from ____ Drug treatment? accumulation of uric acid crystals in extremities (joint of big toe is particularly susceptible. --urate crystals may appear in kidney stones and obstruct urinary tract allopurinol, inhibits Xanthine Oxidase from making uric acid from hypoxanthine
Gout can be exacerbated by ____ purine rich foods
Purine-Nucleotide cycle exhibits anaplerosis by _____ In what tissue is this process particularly important? releases FUMARATE for TCA cycle Contraction of SKELETAL MUSCLE: as AMP builds up, it is converted IMP then back to AMP with release of fumarate which provides more substrate for TCA cycle and stimulates oxidative metabolism for more energy
Lesch-Nyhan Syndrom results from a complete deficiency in ____ Presentation? HGPRT (so can't salvage purines from production and excretion of uric acid); severe hyperuricemia -severe, crippling arthritis due to accumulation of uric acid -retardation -self-mutilation/aggression
HGPRT (hypoxanthine-guanine phosphoribosyltransferase) = ? HGPRT salvages purine at the stage of hypoxanthine (immediately before it would be converted to Uric acid and excreted) adds ribose onto hypoxanthine (using alpha-PRPP) and converts to IMP or GMP
SCID is a group of related disorders involving _______ 30% of SCID patients lack the enzyme ______. In the absence of this enzyme, deoxyadenosine is not deaminated to ______ as normal diminished immune response adenosine deaminase deoxyinosine
Created by: erinlwilliams