Phosphorylation sites of sepiapterin reductase (SPR) phosphorylated by Ca 2+ -dependent protein kinase II (CaM KII) were studied. By immunoreaction against phosphorylated amino acids, we found that Ser residues of SPR were phosphorylated. We constructed several point mutants of SPR by site-directed mutagenesis and expressed then in E. coli. In assays with anti-phospho Ser antibody, we determined that each of the three Ser residues, S46, S 196, and S214, of SPR was phosphorylated by CaM KIl. Each of these serine residues in SPR was found in a CaM KII phosphorylation site sequelce (Arg-X-X-Ser/Thr).
Evidence accumulates suggesting that the pathogenesis in systemic lupus erythematosus (SLE) is associated with modulations in the Fas/FasL system. Serum concentrations of soluble Fas ligand (sFasL) were found to be elevated in patients with SLE. In this study we wanted to determine the levels of sFasL and the status of immune activation - monitored by neopterin secretion - in patients with SLE and cutaneous discoid lupus erythematosus (CDLE). Sixty-five serum samples were assayed. We found elevated concentrations of sFasL in patients with SLE and CDLE. The levels of sFasL in COLE patients were significant lower compared to SLE patients. Neopterin concentrations in serum were found to be slightly increased in patients with CDLE. Compared to patients with SLE, activation of the immune system was significant lower in COLE. Taken together, we found d evated levels of sFasL in patients with SLE as well as CDLE, connected with ar activation of the immune system and thereby increased concentration of neopterin in serum.
Dihydroneopterin has recently been shown to either promote or decrease formation of free radicals or radicalmediated reactions, depending on the conditions. We report here the scavenging activity of dihydroneopterin on nitrogen centered radicals. Diphenylpicrylhydrazyl (DPPH) and tl. e radical cation of 2,2' -azino-di-[3- ethylbenzthiazoline sulphonate] (ABTS) were used. Dihydroneopterin showed scavenging properties against either compound. In the case of DPPH radical scavenging by dihydroneopterin was comparable with trolox. In the ABTS system, dihydroneopterin had an even better capacity of radical scavenging as compared to trolox .
In 40 cataract patients and in 51 patients without pseudoexfoliation (PES) we determined serum concentrations of neopterin, kynurenine, and selenium and concentrations of neopterin in aqueous humour from the anterior chamber of the eye. In addition, selenium content in lenses was determined. Significantly increased kynurenine and neopterin concentrations in serum and neopterin concentrations in aqueous humour were observed in mature cataract patients with PES compared to those without. These patients also presented with the lowest content of selenium in serum and lens, compared with cataract patients without PES. Increased concentrations of neopterin in serum and aqueous humour of the anterior chamber of eyes suggest an increased degree of oxidative stress in patients with PES. Thus, the results support the role of oxidative stress in the development of PES in cataract patients. The decreased content of selenium may elicit immune system activation via an increased oxidative stress as it is indicated by the increased formation of kynurenine and neopterin.
The photoinduced cleavage of plasmid DNA by UV -A light in the presence of pterin was investigated. Electrophoretic analysis of the irradiated plasmid pUCI8 in the presence of pterin showed that UV light of 350 nm induced the transformation of a significant proportion of the supercoiled plasmid to its relaxed form. A minor proportion of plasmid forms are also converted to the linear plasmid isomer at the longer irradiation times. All these transformations during irradiation can be observed in the absorption spectrum of DNA as function of time. Such spectral modifications correlated with the extent and the kinetics of plasmid relaxation, but not with the appearance of the linear plasmid. None of the exchanges were operative without the irradiation with UV-A light. Control experiments with pterin or plasmid DNA irradiated separately, showed no photochemical changes. Results taken together suggest that the observed changes in the supercoiled plasmid as well as the spectral modifications both derive from the generation of single-strand break in the DNA.
