Question

urea cycle first enzyme

Answer 1

The urea cycle is a series of reactions that converts toxic ammonium into the non-
toxic nitrogen excretion production urea. The urea cycle requires ornithine as a
carbon backbone, and aspartate and free ammonium as nitrogen donors.
The free ammonium used in the urea cycle is largely released from glutamate by
glutamate dehydrogenase. This reaction occurs in the mitochondria. The carbamoyl
phosphate synthetase I and ornithine transcarbamoylase reactions also occur in the
mitochondria, allowing the ammonium to be handled under controlled conditions.
The remaining reactions of the urea cycle, however, occur in the cytoplasm.
The urea cycle is regulated by substrate availability and by the enzyme carbamoyl
phosphate synthetase I, which is regulated by N-acetylglutamate. Both N-acetyl-
glutamate and ornithine are synthesized from glutamate.
Nitrogen is normally transported around the body in the form of amino acids. The
amino acids glutamine and alanine are especially important nitrogen transport
molecules. Many tissues incorporate excess nitrogen into glutamine for transport to
the liver and kidney. The muscle prefers to use alanine; the alanine cycle allows the
muscle to obtain rapidly accessible energy from the liver in the form of glucose
while exporting excess nitrogen.
Urea is the major nitrogen excretion product in humans. Free ammonium is also
used to excrete nitrogen, under conditions where proton excretion is also necessary.
Excretion of both ammonium and urea requires large amounts of water; individuals
on high protein diets are at risk for potentially serious dehydration unless they
drink large amounts of fluids.

Answer 2

Hey mate here is your answer》 》


The urea cycle requires five reactions (of which four are part of the actual cycle). The first reaction is the primary regulated step. Carbamoyl phosphate synthetase I5 is the mitochondrial enzyme that catalyzes the formation of carbamoyl phosphate from inorganic ammonium and carbonate.

Hope this answer will help you...《《