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The use of nucleotides and their analogs in the pharmacological studies of nucleo­tide receptors (P2 class) should be preceded by detailed studies on their degradation connected with ecto-enzymes of a given cell type. In the present studies we have ana­lyzed stability of some phosphorothioate and phosphonate analogs of ATP and ADP in the HeLa epitheloid carcinoma and endothelial HUVEC cells cultures. Our studies have revealed that ecto-nucleotide pyrophosphatase (E-NPP) is one of the main en­zymes involved in the extracellular degradation of ATP and other nucleotides in the HeLa cells. On the other hand, the ecto-ATPDase is responsible for the hydrolysis of extracellular nucleotides in human endothelial cell cultures, while the E-NPP-like en­zymes of the HUVEC cells are not essential to this degradation. The concerted action of the aforementioned ecto-enzymes and nucleotide pyrophosphatase, 5 -nucleo- tidase and adenosine deaminase present in fetal bovine serum (FBS) supplied to the culture medium, results in partial or complete degradation of the phosphorothioate (ATPγS) and phosphonate analogs of adenosine nucleotides (α,β-methylene-ATP and β,γ-methylene-ATP) in the cell cultures. Only ADPβS appears to be resistant to these enzymes. The influence of some nucleotides and their analogs on the proliferation of the HeLa cells in presence or absence of FBS is also discussed.
Acetobacter xylinum strains are known as very efficient producers of bacterial cellulose which, due to its unique properties, has great application potential. One of the most important problems faced during cellulose synthesis by these bacteria is generation of cellulose non-producing cells, which can appear under submerged culture conditions. The reasons of this remain unknow. These studies have been undertaken to compare at the molecular level wild-type, cellulose producing (Cel+) A. xylinum strains with Cel- forms of cellulose-negative phenotype. Comparison of protein profiles of both forms of A. xylinum by 2D electrophoresis allowed for the isolation of proteins which were produced exclusively by either Cel+ or Cel- cells. Sequences of peptides derived from these proteins were aligned with those of proteins deposited in databases. This analysis revealed that Cel- cells lacked two enzymes: phosphoglucomutase and glucose-1-phosphate uridylyltransferase, which generates UDP-glucose being the substrate for cellulose synthase. DNA was analyzed by ligation-mediated PCR carried out at low denaturation temperature (PCR-MP). Two DNA fragments of different thermal stability (218 and 217 bp) were obtained from the DNA of Cel+ and Cel- forms, respectively. The only difference between these Cel- and Cel+ DNA fragments is deletion of one T residue. Alignment of those two sequences with those deposited in the GenBank database revealed that similar fragments are present in the genomes of some bacterial cellulose producers and are located downstream from open reading frames (ORF) encoding phosphoglucomutase. The meaning of this observation is discussed.
Dimethoxytritylphosphono-oligonucleotide conjugates have been prepared. They are totally resistant to nucleases present in human serum and do not affect cleavage of a complementary oligoribonucleotide by RNase H. Conjugates possessing a phosphate backbone gave better antisense inhibition of expression of plasminogen activator inhibitor type-1 within endothelial cells as compared with unconjugated oligonucleotides.
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