期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1971
卷号：68
期号：12
页码：3054-3058
DOI：10.1073/pnas.68.12.3054
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A heritable connective tissue disorder of cattle, dermatosparaxis, is characterized by an extreme fragility of the skin and the presence of additional peptides at the N-terminal extremities of the collagen chains, p-1 and p-2. The existence of an enzyme activity is demonstrated in normal connective tissues that is capable of cleaving these additional N-terminal peptides from dermatosparaxic collagen. The activity is demonstratable with dermatosparaxic collagen in solution, as well as with reconstituted dermatosparaxic collagen fibrils polymerized in vitro. It has a pH optimum of about 7.0 and is inhibited by EDTA and mercaptoethanol. Differences in Km and Vmax values exist depending on the substrate utilized, i.e., p-1 or p-2; and the presence of additional amounts of one substrate, p-1, alters the concentration requirement for the second substrate, p-2. The product of the excision reaction with p-1 as substrate is an equimolar amount of normal 1 monomer; the product when p-2 is substrate is an equimolar amount of normal 2 monomer. The enzyme is present in normal calf skin, tendon, aorta, cartilage, and lung; it can be demonstrated in the skin of rats and humans. The enzyme activity is absent in dermatosparaxic connective tissues, thus suggesting that dermatosparaxis is caused by the absence of a normal enzyme function rather than by the production of an abnormal collagen.
