Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

Valproate, or Depakote, can cause encephalopathy in individuals in which this pathway is defective, and CSPI deficiency is a particularly severe disorder affecting this pathway. Disorders in this pathway may be treated with sodium phenylbutyrate, which is metabolized to phenylacetate in the body. One enzyme in this pathway is an isomer of an enzyme that makes up part of the CAD complex in pyrimidine biosynthesis; that enzyme is allosterically regulated by N-acetylglutamate and is called CPS-I. In one step in this pathway, carbamyl phosphate is combined with ornithine to produce citrulline. Originally discovered by Henseleit and Krebs, for 10 points, name this cycle which is used to remove nitrogen from unneeded amino acids from the body.
Science