In vivo labeling and turnover of prolyl hydroxylase and a related immunoreactive protein.

Prolyl hydroxylase and an immunologically related protein (CRP) were purified from neonatal rabbit skin at various time periods following administration of 3H-leucine. The peak incorporation of label into prolyl hydroxylase was found to be 12 hours, while peak incorporation into CRP occurred within 2 hours. Semi-log plots of the loss of radioactivity from these protein pools against time indicated an apparent T 1/2 for prolyl hydroxylase of 78 hours, and a T 1/2 of CRP of 44 hours. Calculated Kd values indicate that that breakdown of active enzyme does not account for the amount of CRP found in tissues.