ornithine carbamoyltransferase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: carbamoyl phosphate + L-ornithine = phosphate + L-citrulline. [EC:2.1.3.3]

Ornithine carbamoyltransferase (OCT) is an enzyme that catalyzes the transfer of a carbamoyl group from carbamoyl phosphate to ornithine, forming citrulline. This reaction is the second step in the urea cycle, a metabolic pathway that converts ammonia, a toxic byproduct of protein metabolism, into urea, which is excreted in urine. OCT is a critical enzyme for nitrogen detoxification and is highly expressed in the liver, the primary site of urea synthesis.

The enzyme is a trimer, with each subunit containing a catalytic site. The active site of OCT contains a highly conserved cysteine residue that is essential for catalysis.

The mechanism of OCT activity involves the following steps:

1. Carbamoyl phosphate binds to the enzyme's active site.
2. The carbamoyl group is transferred to the active site cysteine residue.
3. Ornithine binds to the enzyme.
4. The carbamoyl group is transferred from the cysteine residue to the amino group of ornithine, forming citrulline.
5. Citrulline is released from the enzyme.

The reaction catalyzed by OCT is highly specific for both substrates, carbamoyl phosphate and ornithine. This specificity is due to the unique structure of the active site, which allows for the precise binding and orientation of both substrates.

Deficiency of OCT can lead to hyperammonemia, a serious condition characterized by an accumulation of ammonia in the blood. This can cause neurological damage, coma, and even death. Treatment for OCT deficiency typically involves dietary restrictions and ammonia scavengers.

In addition to its role in urea synthesis, OCT has also been implicated in other biological processes, including cell growth and proliferation. Further research is needed to fully understand the diverse roles of OCT in human health.'
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Proteins (1)

Compounds (4)