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Excretion of phenylpyruvic, 4-hydroxyphenylpyruvic and indolyl-3-acetic acids by the skin fibroblasts from a phenylketonuric child.

High-resolution gas chromatography and mass spectrometry have been used to analyse the changing chemical composition of the culture medium upon the growth of skin fibroblasts from a healthy individual and from a classical phenylketonuric (PKU) patient. The PKU fibroblasts, unlike normal ones, were found to excrete into the culture medium phenylpyruvate, 4-hydroxyphenylpyruvate, indolyl-3-acetate and an unidentified metabolite containing the phenyl group. This testifies to the disturbed metabolism of phenylalanine, tyrosine and tryptophan in the PKU fibroblasts. This seems to be the reason for their reduced viability as compared with normal fibroblasts.

Adult↗

Beta-phenylpyruvate and glucose uptake in isolated mouse soleus muscle and cultured C2C12 muscle cells.

Previous investigation demonstrated the potential of beta-phenylpyruvate at high concentration to cause hypoglycemia in mice totally deprived of insulin. For further elucidation of the glucose-lowering mechanism, glucose uptake, and quantity of glucose transporters (GLUT1 and GLUT4) in mouse soleus muscle and C2C12 muscle cell lines were investigated following incubation with beta-phenylpyruvate in various concentrations. A marked enhancement of glucose uptake was demonstrated that peaked at 0.5 and 1.0 mM beta-phenylpyruvate in soleus muscle (P<0.01) and C2C12 cells (P<0.001), respectively. Kinetic analysis in C2C12 cells showed a twofold increase in Vmax compared with controls (P<0.001). In addition, both GLUT1 and GLUT4 levels were increased following exposure to beta-phenylpyruvate. Our findings point to a peripheral hypoglycemic effect of beta-phenylpyruvate.

Animals↗

Automated generation of MCSS-derived pharmacophoric DOCK site points for searching multiconformation databases.

All docking methods employ some sort of heuristic to orient the ligand molecules into the binding site of the target structure. An automated method, MCSS2SPTS, for generating chemically labeled site points for docking is presented. MCSS2SPTS employs the program Multiple Copy Simultaneous Search (MCSS) to determine target-based theoretical pharmacophores. More specifically, chemically labeled site points are automatically extracted from selected low-energy functional-group minima and clustered together. These pharmacophoric site points can then be directly matched to the pharmacophoric features of database molecules with the use of either DOCK or PhDOCK to place the small molecules into the binding site. Several examples of the ability of MCSS2SPTS to reproduce the three-dimensional pharmacophoric features of ligands from known ligand-protein complex structures are discussed. In addition, a site-point set calculated for one human immunodeficiency virus 1 (HIV1) protease structure is used with PhDOCK to dock a set of HIV1 protease ligands; the docked poses are compared to the corresponding complex structures of the ligands. Finally, the use of an MCSS2SPTS-derived site-point set for acyl carrier protein synthase is compared to the use of atomic positions from a bound ligand as site points for a large-scale DOCK search. In general, MCSS2SPTS-generated site points focus the search on the more relevant areas and thereby allow for more effective sampling of the target site.

Binding Sites↗

Effects of phenylalanine and its deaminated metabolites on Na+,K+-ATPase activity in synaptosomes from rat brain.

The effects of phenylalanine (PHE) and its deaminated metabolites phenylpyruvate (PHP), phenyllactate (PHL) and phenylacetate (PHA) on sodium and potassium activated adenosinetriphosphatase (Na+,K+-ATPase) in synaptosomes from rat brain were investigated. At very low concentrations (5-10 microM). PHE, PHL and PHA inhibited the activity, while PHP stimulated the activity. At intermediate concentrations (50-100 microM), all compounds had no effect, but at higher (0.5-1.0 mM) concentrations they inhibited the enzyme activity. Thus all the compounds tested showed a biphasic effect on the enzyme activity. Hydroxylamine inhibited the Na+,K+-ATPase activity when present alone; simultaneous addition of hydroxylamine and PHE, however, eliminated the inhibitory effects of each other. Reversal of mutual inhibition also occurred in the presence of hydroxylamine and very low (5-10 microM) concentrations of PHL or PHA. The inhibitory effects of PHE at aLl concentrations, and of PHL or PHA at low concentrations, were also eliminated in the presence of EGTA. The data indicate that inhibition of brain membrane Na+,K+-ATPase by PHE and by low concentrations of PHL and PHA may involve metal ions, but that the inhibition by high concentrations of these metabolites must occur by a different mechanism. Since Na+,K+-ATPase plays a central role in neuronal function, and the presence of excess PHE and its deaminated metabolites occurs in brain tissue under conditions of experimentally induced hyperphenylalaninemia and genetic phenylketonuria, the neurologic impairment in experimental and genetic PKU may in part be related to the deleterious effects of these compounds on brain ATPase.

Animals↗

Effects of phenylalanine and phenylpyruvate on ATP-ADP hydrolysis by rat blood serum.

The nucleotide (ATP-ADP)/nucleoside (adenosine) ratio in the circulation can modulate the processes of vasoconstriction, vasodilatation and platelet aggregation. The main objective of the present study with rat blood serum was to evaluate the possibility of changes in nucleotide hydrolysis by phenylalanine (Phe) and phenylpyruvate (PP), the levels of which could increase in the circulation of individuals with phenylketonuria. Results demonstrated that Phe in the range 1.0-5.0 mM inhibited the ADP hydrolysis by rat serum. The effect of inhibition by Phe on ATP hydrolysis appeared only at a concentration of 5.0 mM. PP had no significant effect upon nucleotide hydrolysis. Kinetic analysis indicated that the inhibition of ADP and ATP hydrolysis by Phe in rat blood serum is uncompetitive. Conversely, Phe and PP did not affect the hydrolysis of p-nitrophenyl-5'-TMP by rat serum.

Adenosine Diphosphate↗