Protocollagen proline hydroxylase in skin and muscle of some vertebrate species

Protocollagen proline hydroxylase activity was studied in skin and muscle of poikilothermic and homoiothermic animals. Lower PPH activity was found in the former than in the latter. Increased PPH activity was found in skin of young Gallus domesticus and Rattus norvegicus. In specialized skin under hormonal control, i.e. comb and wattles, increased activity in relation to sexual maturation was shown. The PPH activity in muscles of poikilotherms was lower than in those of homoiotherms. Some of the muscles had a considerable enzymatic activity. A decreasing PPH activity was noticed in birds and mammals with age. Heart muscle had more hydroxylating activity than skeletal muscle.