Prolyl and lysyl hydroxylase activation and cofactor specificity in young and senescent WI-38 fibroblast cultures.

The activation of prolyl hydroxylase and lysyl hydroxylase by ascorbate was studied in young and senescent WI-38 fibroblast cultures using a tritium-release assay. Prolyl hydroxylase activity could be increased 3–4 fold in young cultures but remained unchanged in senescent cultures when these cultures underwent a two-hour preincubation in medium containing 0.2mM sodium ascorbate. Lysyl hydroxylase levels were unaffected both in young and senescent cultures. In another series of experiments, ascorbate was replaced with several other compounds in the tritium-release assay demonstrating that this reducing agent is not a specific cofactor of the partially purified enzymes from WI-38 cultures.