Thymidine phosphorylase activity of platelet-derived endothelial cell growth factor is responsible for endothelial cell mitogenicity.
Recombinant human platelet-derived endothelial cell growth factor, expressed in the yeast Saccharomyces cerevisiae was purified to greater than 98% purity by anion-exchange and hydroxyapatite chromatography. It was shown to possess thymidine phosphorolytic activity in vitro (pH optimum, pH 5.3; Km, 0.11 mM; Vmax, 12.5 mmol min-1 mg-1; turnover number, 9.4 s-1). Covalent modification simultaneously inhibited the enzymatic and mitogenic properties of the protein, while interaction with a cell-surface receptor was not required to stimulate mitogenesis. Purified Escherichia coli thymidine phosphorylase was also mitogenic toward endothelial cells. It is proposed that platelet-derived endothelial cell growth factor is human thymidine phosphorylase which promotes endothelial cell proliferation by reducing thymidine levels that would otherwise be inhibitory to endothelial cell growth.
Finnis
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C
Delta Biotechnology Limited, Nottingham, England.
Dodsworth
N
N
Pollitt
C E
CE
Carr
G
G
Sleep
D
D
D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects*; D004926:Escherichia coli / Q000201:enzymology; D006801:Humans; D008934:Mitogens / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013939:Thymidine Phosphorylase / Q000378:metabolism / Q000494:pharmacology*
D008934:Mitogens; D011994:Recombinant Proteins; D004247:DNA; D013939:Thymidine Phosphorylase