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：1972
卷号：69
期号：10
页码：2910-2913
DOI：10.1073/pnas.69.10.2910
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Evidence has been obtained that a single protein, known to modulate classical complement activation, also acts as an inhibitor in the properdin or alternate complement pathway. A highly purified inactivator of the third component of complement (C3) from human serum inhibited the proteolysis of Factor B in the properdin system (glycine-rich {beta}-glycoprotein) by glycine-rich {beta}-glycoproteinase. The inhibition was by the enzymatic destruction of glycine-rich {beta}-glycoproteinase activity. The major fragment of C3, C3b, which is the only known substrate of the C3 inactivator, blocked the destruction of glycine-rich {beta}-glycoproteinase by the C3 inactivator. Thus, in its inhibition of the porperdin pathway, the C3 inactivator destroys both the active form of glycine-rich {beta}-glycoproteinase and a protein involved in the conversion of the zymogen form of this enzyme (proglycine-rich {beta}-glycoproteinase) to its active form. The increased susceptibility to infections in a patient homozygous for deficiency of the C3 inactivator demonstrates the biologic significance of this protein.
