Human lysyl hydroxylase: purification to homogeneity, partial characterization and comparison of catalytic properties with those of a mutant enzyme from Ehlers-Danlos syndrome type VI fibroblasts.

Lysyl hydroxylase was isolated as an essentially homogeneous protein from human fetal tissues and as a homogeneous protein from placental tissue by a procedure involving ammonium sulfate fractionation, affinity chromatography on concanavalin A-agarose, affinity chromatography on collagen linked to agarose and gel filtration. The specific activity of the best enzyme preparations from human fetal tissues was about 80,000 times, and from human placenta about 63,000 times that in the 15,000 X g supernatant of the corresponding tissue homogenate. The molecular weight of lysyl hydroxylase from both sources was about 190,000 by gel filtration, and that of the enzyme subunit about 85,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The specific activity and molecular properties reported are very similar to those of pure chick-embryo lysyl hydroxylase, and the Km values for type I protocollagen substrate, and synthetic peptide substrate and all the co-substrates of the human placenta enzyme are likewise very similar to those of the chick-embryo enzyme. No difference in the Km values for type I protocollagen or any of the co-substrates was found between the human placenta enzyme and a crude lysyl hydroxylase from the skin fibroblasts of a patient with the type VI variant of the Ehlers-Danlos syndrome.