Nucleoside-catabolizing enzyme activities in primary rabbit kidney cells and human skin fibroblasts

Abstract

Primary rabbit kidney (PRK) and human skin fibroblast (HSF) cell cultures, two cell systems which are regularly employed in our laboratory to explore the antiviral properties of nucleoside analogues, were analyzed for the specific activities of the following nucleoside catabolizing enzymes: cytidine deaminase (EC 3.5.4.5), pyrimidine nucleoside phosphorylases (uridine phosphorylase: EC 2.4.2.3, and 2′-deoxythymidine phosphorylase: EC 2.4.2.4), purine nucleoside phosphorylase (EC 2.4.2.1) and adenosine deaminase (EC 3.5.4.4). No cytidine deaminase activity was detected in either PRK or HSF cells. Likewise, no 2′-deoxythymidine phosphorylase activity could be demonstrated in PRK and HSF cells. PRK cells contained low levels of uridine phosphorylase (3–;5 U/mg protein) and high levels of purine nucleoside phosphorylase (∼ 100 U/mg protein). For both PRK and HSF cells, relatively high adenosine deaminase activities were recorded (at an average 20 and 36 U/mg protein, respectively). Infection of the PRK or HSF cell cultures with either vaccinia virus, herpes simplex virus (type 1 or 2) or vesicular stomatitis virus at high multiplicity of infection (MOI ∼ 1) did not bring about marked changes in any of the enzymatic activities tested. For uridine phosphorylase (from PRK cells) and adenosine deaminase (from both PRK and HSF cells) the substrate specificities were determined with various uridine and adenosine analogues.