SPECIFICITIES OF PROTOCOLLAGEN HYDROXYLASES FROM DIFFERENT SOURCES

1. 1. Protocollagen hydroxylase from calf embryo skin is able to hydroxylate only proline residues in position I of synthetic (l-Pro-Gly-l-Pro)n substrates. 2. 2. The corresponding enzyme from earthworm body wall is less specific. It converts proline residues in both position 1 and 3 of the polymeric tripeptide substrates to hydroxyproline. In both positions a high amount of 3-l-Hyp is synthesized besides the 4-isomer. 3. 3. When protocollagen is used as a substrate, 3-hydroxyproline is formed by both hydroxylases. The amounts are close to the values of 3-Hyp found in the collagens of the respective tissues from which these enzymes were extracted. 4. 4. Hydroxylase preparations from both sources lose half of their activity when once frozen and thawed. The original level of activity may be restored by addition of α-ketoglutarate. © 1969.