Prolyl and lysyl hydroxylase activities of human skin fibroblasts: effect of donor age and ascorbate.

Prolyl and lysyl hydroxylase activities in cultures of human skin fibroblasts from fetal to 94-yr-old donors were measured. In contrast to earlier studies with whole skin, neither prolyl nor lysyl hydroxylase activity was found related to donor age. Prolyl hydroxylase activity increased 3- to 6-fold when cell extracts were incubated with ascorbate and other hydroxylation cofactors before assay. A similar increase in prolyl hydroxylase activity occurred when cells were incubated with ascorbate. Lysyl hydroxylase activity remained unaltered under these conditions.