Lapière C M, Lenaers A, Kohn L D
Proc Natl Acad Sci U S A. 1971 Dec;68(12):3054-8. doi: 10.1073/pnas.68.12.3054.
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 alpha chains, p-alpha(1) and p-alpha(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 K(m) and V(max) values exist depending on the substrate utilized, i.e., p-alpha(1) or p-alpha(2); and the presence of additional amounts of one substrate, p-alpha(1), alters the concentration requirement for the second substrate, p-alpha(2). The product of the excision reaction with p-alpha(1) as substrate is an equimolar amount of normal alpha(1) monomer; the product when p-alpha(2) is substrate is an equimolar amount of normal alpha(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.
牛的一种遗传性结缔组织疾病——皮肤松弛症，其特征是皮肤极度脆弱，且在胶原蛋白α链（p-α(1)和p-α(2)）的N末端存在额外的肽段。在正常结缔组织中已证实存在一种酶活性，该酶能够从皮肤松弛症胶原蛋白中切割掉这些额外的N末端肽段。这种活性在溶液中的皮肤松弛症胶原蛋白以及体外聚合的重组皮肤松弛症胶原纤维中都可得到证明。其最适pH约为7.0，且受EDTA和巯基乙醇抑制。根据所使用的底物（即p-α(1)或p-α(2)）不同，K(m)和V(max)值存在差异；并且一种底物p-α(1)的额外存在会改变对第二种底物p-α(2)的浓度需求。以p-α(1)为底物的切除反应产物是等摩尔量的正常α(1)单体；以p-α(2)为底物时，产物是等摩尔量的正常α(2)单体。该酶存在于正常小牛的皮肤、肌腱、主动脉、软骨和肺中；在大鼠和人类的皮肤中也可检测到。在皮肤松弛症的结缔组织中不存在这种酶活性，因此表明皮肤松弛症是由正常酶功能的缺失而非异常胶原蛋白的产生所引起的。
