Studies on the mechanism of reduction of prolyl hydroxylase activity by D,L-3,4 dehydroproline.

When chick frontal bone cells in culture were exposed to d,l-3,4 dehydroproline, the specific activity of prolyl hydroxylase was markedly reduced, but the concentration of the protein antigenically related to prolyl hydroxylase was not decreased. The specific activity of purified prolyl hydroxylase from cells grown in d,l-3,4 dehydroproline was significantly lower than that of control cells. Preincubation of a homogeneous preparation of chick embryo prolyl hydroxylase with collagenous peptides containing [¹⁴C]d,l-3,4 dehydroproline resulted in a time-dependent decrease in the enzymatic activity. These observations suggest that the in vivo reduction in prolyl hydroxylase activity by dehydroproline could be either due to an interaction of the enzyme with collagenous peptides containing dehydroproline and/or the synthesis of an aberrant form of prolyl hydroxylase with decreased enzymatic activity.