The novel type II prolyl 4-hydroxylase is the main enzyme form in chondrocytes and capillary endothelial cells, whereas the type I enzyme predominates in most cells.
Procollagen-proline dioxygenase (EC 1.14.11.2), an alpha2beta2 tetramer in vertebrates, plays a central role in the synthesis of all collagens. Recently an isoform of the alpha subunit, the alpha(II) subunit, was characterized in man and mouse and found to form a tetramer with the same beta subunit as the previously known alpha(I) subunit. We report here that the (alpha(I))2beta2 type I tetramer is the main enzyme form in most cell types and tissues and that its contribution to total prolyl 4-hydroxylase activity in cultured cells increases in confluence. Surprisingly, however, the (alpha(II))2beta2 type II enzyme was found to represent at least about 70% of the total prolyl 4-hydroxylase activity in cultured mouse chondrocytes and about 80% in mouse cartilage, the corresponding percentage in mouse bone being about 45% and that in many other mouse tissues about 10% or less. Immunofluorescence studies on samples from a fetal human foot confirmed these data and additionally indicated that the type II enzyme represents the main or only enzyme form in capillary endothelial cells. Thus the type II prolyl 4-hydroxylase is likely to play a major role in the development of cartilages and cartilaginous bones and also of capillaries.
Annunen
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P
Collagen Research Unit, Biocenter and Department of Medical Biochemistry, University of Oulu, FIN-90220 Oulu, Finland.
Autio-Harmainen
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H
Kivirikko
K I
KI
D000818:Animals; D002196:Capillaries / Q000166:cytology / Q000201:enzymology*; D019902:Chondrocytes / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000201:enzymology*; D005333:Fetus / Q000201:enzymology; D005528:Foot / Q000502:physiology; D006801:Humans; D007527:Isoenzymes / Q000032:analysis*; D051379:Mice; D011393:Procollagen-Proline Dioxygenase / Q000032:analysis*; D014018:Tissue Distribution
D007527:Isoenzymes; D011393:Procollagen-Proline Dioxygenase