Sapropterin, also known as tetrahydrobiopterin (BH4), is a naturally occurring substance in the human body that plays a crucial role in the synthesis of neurotransmitters and the degradation of phenylalanine [1][2]. Sapropterin is not synthesized in the body as a standalone compound, but rather, it is a cofactor involved in various biochemical reactions [3].

Sapropterin is synthesized through a series of enzymatic reactions involving several intermediates [3]. The synthesis of sapropterin begins with the formation of guanosine triphosphate (GTP) from guanosine diphosphate (GDP) [3]. GTP is then converted to dihydroneopterin triphosphate (DPTH) through a series of reactions involving the enzymes GTP cyclohydrolase I and 6-pyruvoyltetrahydropterin synthase [3]. DPTH is subsequently reduced to form tetrahydrobiopterin (sapropterin) [3].

Sapropterin is used as a medication for the treatment of phenylketonuria (PKU), a genetic disorder characterized by a deficiency in the enzyme phenylalanine hydroxylase, which leads to an accumulation of phenylalanine in the body [1]. Sapropterin helps to lower phenylalanine levels by promoting the activity of phenylalanine hydroxylase [1].

In summary, sapropterin is not synthesized as a standalone compound in the body, but rather, it is a cofactor involved in various biochemical reactions. Sapropterin is synthesized through a series of enzymatic reactions involving several intermediates, starting with the formation of GTP. Sapropterin is used as a medication for the treatment of PKU.

Sources:

[1] <https://www.drugpatentwatch.com/p/tradename/SAPROPTERIN>

[2] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6769157/>

[3] <https://pubmed.ncbi.nlm.nih.gov/17968763/>