Deficiency of a Urea Cycle Enzyme Results in Excretion of Pyrimidine Precursors

Increased excretion of orotic acid, uracil, and uridine accompanies a deficiency in liver mitochondrial or-nithine transcarbamoylase (reaction 2, Figure 29-9).

Cytosine

NADP+

Hf>H

Thymine

NADP+

Hf>H

Dihydrouracil

COO-

h2n ^ch2

HN^N<Chl3

Dihydrothymine

-H2O

COO-

P-Ureidopropionate p-Ureidoisobutyrate

(w-carbamoyl-p -alanine) (w-carbamoyl-p -amino-

isobutyrate)

CO2+ NH

CO2+ NH

P -Alanine

Figure 34-9. Catabolism of pyrimidines.

P -Aminoisobutyrate

Excess carbamoyl phosphate exits to the cytosol, where it stimulates pyrimidine nucleotide biosynthesis. The resulting mild orotic aciduria is increased by high-nitrogen foods.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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