Activation of prolyl hydroxylase in tissue homogenates of scorbutic guinea pigs.

Prolyl hydroxylase activity was measured in a variety of tissues from scorbutic and control guinea pigs. The activity of the enzyme was lower in skin, induced granuloma, aorta, arteries and lung of scorbutic animals. However, in liver and kidney the enzyme levels were the same or higher than in control animals. The low prolyl hydroxylase activity in the former tissues could be increased by incubating the homogenates with all the cofactors of prolyl hydroxylase such as ascorbate, ferrous ions and alpha-ketoglutarate, prior to the assay. An incubation time of 2-3 hours at 30 degrees was needed for optimal activation. The low enzyme activity in scorbutic animals was not due to the competition of underhydroxylated collagen present in the homogenate with the radioactive substrateused in the assay. Moreover, unlike in the control animals, the enzyme derived from granuloma of scorbutic animals was highly resistant to dithiothreitol inactivation. These data suggest that some tissues of scorbutic guinea pigs contain a prolyl hydroxylase which is an activatable form.