Pterins urine

Screening for a BH4 deficiency should be done in all newborns with plasma phenylalanine levels higher than 120 pmol/1, as well as in older children with neurologic signs and symptoms [10]. The following tests are recommended (1) analysis of pterins in urine, (2) measurement of DHPR activity in blood from a Guthrie card,... 

Analysis of Pterins in Urine, Plasma, Blood Spots,... 

Native urine should be protected from light and stored at -20°C until processed. Oxidized urine sample can be stored at room temperature, but light protection is still recommended. Two procedures for the oxidation of urine (and other samples) are used (1) oxidation with manganese dioxide (Mn02) under acidic conditions, and (2) oxidation with iodine (iodine/potassium iodide, I2/KI) under acidic and basic conditions. The Mn02 oxidation method is a routine method used to quantify total pterins (fully oxidized neopterin, monapterin, biopterin, primapterin, isoxanthopterin, and pterin) the I2/KI method is used according to Fukushima and Nixon [11] for the differential oxidation of pterins and quantification of BH4. Total biopterin represents the sum of BH4, BH2, and fully oxidized biopterin. Under acidic conditions BH4 and BH2 are oxidized to biopterin, while under basic conditions only BH2 is oxidized to... 

Urine standard mixture pipette the volumes given in Table 6.1.2 of 0.001% pterin working solutions in a 20-ml flask and fill with 0.05 M HC1 to the mark. Store aliquots at -20°C. 

Table 6.1.2 Volumes of 0.001% pterins working solutions required to make up urine standard mixtures...

A Fig. 6.1.7a- HPLC of pterins using a column-switching system a standard mixture b control urine c urine guanosine triphosphate cyclohydrolase I (GTPCH) deficiency d urine 6-pyru-voyl-tetrahydropterin synthase (PTPS) deficiency e urine pterin-4a-carbinolamine dehydratase (PCD) deficiency f urine dihydropteridine reductase (DHPR) deficiency g urine phenylketonuria 4-8 h after tetrahydrobiopterin (BH4) administration h-k see next page... 

Figure 6.1.7 b-f shows chromatograms of pterins in urine from patients with different enzyme defects of BH4 metabolism, and Fig. 6.1.7 h-k chromatograms of pterins in dried blood. The pattern of pterins in plasma, dried blood, and CSF is similar to that in urine in patients with BH4 deficiency. Only urine and dried blood spots are suitable for screening. For more details see Blau et al. [13]. 

Reference pterin values for urine, serum, and CSF are given in Table 6.1.5. Those for amniotic fluid and dried blood are given in Table 6.1.6. 

Table 6.1.5 Reference values for pterins in urine, serum, and cerebrospinal fluid. Bio biopterin, CSF cerebrospinal fluid, Neo neopterin, S serum, Sep sepiapterin, U urine...

First isolated from human urine, biopterin (Fig. 15-17) is present in liver and other tissues where it functions in a reduced form as a hydroxylation coenzyme (see Chapter 18).338 It is also present in nitric oxide synthase (Chapter 18).341/342 Other functions in oxidative reactions, in regulation of electron transport, and in photosynthesis have been proposed.343 Neopterin, found in honeybee larvae, resembles biopterin but has a D-erythro configuration in the side chain. The red eye pigments of Drosophila, called drosopterins, are complex dimeric pterins containing fused 7-membered rings (Fig. 15-17).344 345... 

PCD deficient patients excrete 7-biopterin (137), called primaterin, in their urine [152-154], which had not been observed in normal mammals. The mechanism of the 7-substituted pterin synthesis from 6-substitute has been proposed [155,156] (Scheme 33). When 95 is rapidly dehydrated to 45 via PCD, the dihydroxypropyl side chain of 95 is retained at its 6-position. However, in the absence of PCD activity, the rate of conversion of unstable 95 is slow. Therefore, its pyrazine ring is opened to give 98, and recyclization of 98 to the 7-substituted pterin derivative proceeds via spiro intermediate 138 [89,156]. 

The evidence for a pterin-substituted 1,2-enedithiolate was first reported by Raja-gopalan, Johnson, and coworkers, who isolated pterins from the oxidative decomposition of molybdenum-bound MPT, Figure 4 [7,49,55,56], In complementary work, Taylor and coworkers confirmed the structure of several of the pterin decomposition products by direct synthesis (see Section V. A) [30,57-59], Urothi-one, first isolated in 1940 from human urine [60], was shown to be a metabolic degradation product of MPT [37], Other isolated pterin-containing decomposition and/or derivatized products from molybdenum enzymes include Form A, Form B (a urothione-like product), and camMPT (Figure 4) [7], Two other pterins, Form Z and the MPT precursor, can be obtained from molybdenum deprived organisms, N. crassa Nit-1, and oxidase-deficient children, neither of which pro-... 

Oncopterin (472), another natural pterin derivative from the urine of cancer patients, was identified as iV2-(3-aminopropyl)biopterin <93MI 718-19), showing again an unusual substitution at the 2-amino group as first noticed for euglenapterin (473) <86LA1705>. 

The modeling and ultimate total synthesis of molybdopterin and Mo-co have been hampered by difficulties associated with the pterin chemistry involved. However, synthetic assaults on molybdopterin, the molybdenum cofactor, and the degradation products of the molybdenum cofactor are now well underway. The total chemical synthesis of urothi-one (7), the postulated metabolic excretory product of Mo-co (25), has recently been reported (4 7). Compound 7 is a naturally occurring substituted thiophene that is found in the urine of normal humans. It is absent (25) from the urine of children who lack the molybdenum cofactor due to a genetic defect and who are unable to metabolize sulfite (48). The absolute configuration of Form A (8), another degradation product of... 

Methylbiopterin and 2 -deoxybiopterin are two naturally occurring pterin-6-yl acyclo C-nucleosides related to biopterin. The former was isolated from methanol extracts of the marine anthozoan Asteroides calycularis Pallas and found to inhibit growth of mouse and chick fibroblasts in culture (87E950), whereas the latter was isolated from urine of patients with malignant lymphoma (95MI2). 

Biopterin (890), a pterin isolated from human urine, is an important precursor of tetra-hydrobiopterin, which is useful in the treatment of Parkinson s disease. The anti-d o arrangement in the side chain is accessible via organometallic addition to a lactaldehyde (Scheme 118). 

A major development in the definition of the constitution of Moco was the recognition that an oxidized, inactive, form of this cofactor has the fluorescence properties characteristic of a pterin. Further studies indicated that the fluorescent materia was derived from a novel, sulfur-containing reduced pterin substituted at the C-6 position.Subsequently, a metabolic relationship was established between Moco and urothione, since persons genetically deficient in Moco are unique in having no detectable urothione in their urine. This metabolic relationship, and the chemical reactions of the cofactor, formed the basis from which Johnson and Rajagopalan proposed a structure (Figure 17) for Moco. ... 

Various pterin derivatives are detected in human urine, and the main components are biopterin and D-erythroneopterin. These are excreted every day, typically in the amount of 980 mg and 380 mg, respectively. It is said that the level of excretion is not changed, even if a large amount of folic acid is administered orally [8]. 

Roethler, F., and Karobath, M. Quantitative Determination of Unconjugated Pterins in Urine by Gas Chromatography/Mass Spectrometry... 

The catabolism of folate is largely by cleavage of the C-9—N-10 bond, catalysed by carboxypeptidase G. The -aminobenzoic acid moiety is amidated and excreted in the urine as -acetamidobenzoate and / -acetamidobenzoyl-glutamate pterin is excreted either unchanged or as isoxanthopterin and other biologically inactive metabolites. 

---