To understand how the absence of this enzyme affects the body, we must look at the BH4 synthesis pathway. PTPS is an intermediate in this cycle and is needed to convert 7,8 - dihydroneopterin triphosphate to<unk> -Pyruvoyltetrahydryobiopterin.<unk> -Pyruvoyltetrahydryobiopterin is converted into BH4 (Tetrahydrobiopterin), but since it stops at<unk> -Pyruvoyltetrahydrobiopterin no BH4 is made. The absence of BH4 affects the metabolism of Phenylalanine. This is the reason that PKU and PTPS deficiency share some similar symptoms. However, since BH4 is needed for much more than just the metabolism of Phenylalanine, there are other symptoms as well. This image depicts the pathway for the synthesis if tetrahydrobiopterin, a very important cofactor in the human body. Structure and function of<unk><unk><unk>  PTPS is a hexamer of identical subunits. The PTPS monomer folds into a sequential four-stranded, antiparallel 𝛃-sheet. Three PTPS monomers form a 12-stranded antiparallel 𝛃-barrel by tight association between the N and C terminus of 2 adjacent subunits. The active enzyme complex is formed by two trimers in a head-to-head fashion. The active site is in between the trimer-trimer interface and has 3 monomers: A, A′, B. There are three histidine residues that form the metal-binding site in the substrate binding pocket: His 23,48 and 50. Residues Cys42, Glu133, and His89 are in close proximity to the binding pocket but are not binding it. These are thought to serve as proton donors and acceptors during catalysis. The cofactor bound can be either Mg2+ or Ni2+ (Protein Database). As previously mentioned it is involved in the biosynthesis of BH4 and catalyzes the transformation of 7,8-dihydroneopterin triphosphate into<unk> -pyruvoyl tetrahydropterin<unk> . The kinetic values for this enzyme are KM = 8.1 μM and Vmax = 120 nmol/min/mg. The structure of PTPS is unique and is different than other examples of antiparallel 𝛃-barrels. It is described as being formed by "a three-fold symmetrical arrangement of subunits". A similar 𝛃-barrel formation has been discovered in CKS2, the difference between PTPS and CKS2 is that the formation of the latter is metal induced and reversible. The PTPS trimer is similar to a porin and is hypothesized to serve as a tunnel for dihydroneopterin triphosphate.
6-Pyruvoyltetrahydropterin synthase deficiency
Arginine:glycine amidinotransferase deficiency
Ribose-5-phosphate isomerase deficiency
Triosephosphate isomerase deficiency
Carbamoyl phosphate synthetase I deficiency
Aldolase A deficiency
Transaldolase deficiency
Malonyl-CoA decarboxylase deficiency